Ch 2 Chemistry the Central Science Flashcards

Terms Definitions
Who was Democritus and what did he theorize?
Democritus (460–370 BC): All matter can be divided into indivisible atomos.
What did Dalton propose and what were his 4 postulates?
proposed atomic theory with the following postulates:
• Elements are composed of atoms.
• All atoms of an element are identical.
• In chemical reactions atoms are not changed into different types of atoms. Atoms are neither
created nor destroyed.
• Compounds are formed when atoms of elements combine.
What are Atoms?
Atoms are the building blocks of matter.
What is the Law of constant composition?
The relative kinds and numbers of atoms are constant for a given
compound.
What is the Law of conservation of mass (matter)?
During a chemical reaction, the total mass before the reaction
is equal to the total mass after the reaction.
What is Conservation?
Conservation means something can neither be created nor destroyed.
What is the Law of multiple proportions?
If two elements, A and B, combine to form more than one compound,
then the mass of B, which combines with the mass of A, is a ratio of small whole numbers.
by 1850 what did scientist learn about atoms?
By 1850 scientists knew that atoms consisted of charged particles.
What are subatomic particles?
Subatomic particles are those particles that make up the atom.
What is the the law of electrostatic attraction?
like charges repel and opposite charges attract.
When were Cathode rays discovered?
Cathode rays were first discovered in the mid-1800s from studies of electrical discharge through
partially evacuated tubes (cathode-ray tubes or CRTs).
What are cathode rays?
Cathode rays = radiation produced when high voltage is applied across the tube.
What does the voltage in a cathode ray tube do to the negatively charged particles?
The voltage causes negative particles to move from the negative electrode (cathode) to the positive
electrode (anode).
How can the path of the electrons be altered in a CRT?
The path of the electrons can be altered by the presence of a magnetic field.
How and when did J. J. Thomson determined the charge-to-mass ratio of an electron?
In 1897 he measured the ratio by seeing how the magnetic field around the cathode ray affected the rays.
What is the Charge to mass ratio of an electron?
Charge-to-mass ratio: 1.76 x 10^8 C/g.
What is a coulomb?
The coulomb (symbol: C) is the SI derived unit of electric charge
What was the goal of Millikan Oil-Drop Experiment?
find the charge on the electron to determine its mass.
How was the Millikan Oil-Drop Experiment carried out?
• Oil drops are sprayed above a positively charged plate containing a small hole.
• As the oil drops fall through the hole they acquire a negative charge.
• Gravity forces the drops downward. The applied electric field forces the drops upward.
• When a drop is perfectly balanced, then the weight of the drop is equal to the electrostatic force
of attraction between the drop and the positive plate.
What is the charge of an electron?
1.60 x 10^(–19) C.
What is the mass of an electron and how was it calculated?
Mass = [ 1.60 x 10^(–19) C.] / [1.76 x 10^8 C/g.]

= 9.10 x 10^(-28) g
What is radioactivity?
Radioactivity is the spontaneous emission of radiation.
What did Marie Curie and Pierre do to help the study of radiation?
Marie Curie and Pierre isolated radioactive components of a mineral
What is an alpha particle and what is its charge?
Alpha particles consist of two protons and two neutrons bound together into a particle identical to a helium nucleus; hence, it can be written as He2+ or 42He2+. Its charge is 2+ because it has 2 protons and no electrons
What is beta particle and what is its charge?
Beta particles are high-energy, high-speed electrons or positrons emitted by certain types of radioactive nuclei. The charge is -1 because it is an electron
What is a gamma ray and what is its charge?
Gamma rays (denoted as γ) are electromagnetic radiation of high energy. They are not affected by electromagnetism thus have no charge.
What is the mass of an alpha particle in comparison to beta particles?
an alpha particle has 7400 times the mass of a beta particle
Who revealed the 3 types of radiation? And how?
Ernest Rutherford revealed 3 types of radiation- alpha, beta, and gamma. He did this by separating radioactive rays using electrically charged plates. Beta particles moved towards the positive end. Alpha particles moved to the negative end. But gamma rays were not affected showing that it had no charge.
What did the Thompson model of an atom look like?
The Thomson model pictures the atom as a sphere with small electrons embedded in a positively
charged mass. Called the plum pudding model
Describe Rutherford's “gold foil” experiment.
A source of a-particles was placed at the mouth of a circular detector.
• The a-particles were shot through a piece of gold foil.
• Both the gold nucleus and the a-particle were positively charged, so they repelled each other.
• Most of the a-particles went straight through the foil without deflection.
How did Rutherford modify Thompson's model?
• Assume the atom is spherical, but the positive charge must be located at the center with a diffuse
negative charge surrounding it.
• In order for the majority of a-particles that pass through a piece of foil to be undeflected, the
majority of the atom must consist of a low mass, diffuse negative charge -- the electron.
• To account for the small number of large deflections of the a-particles, the center or nucleus of the atom must consist of a dense positive charge.
When did Rutherford discover the nucleus?
In 1911
What is a nucleus?
The nucleus is the very dense region consisting of nucleons (protons and neutrons) at the center of an atom
Who discovered protons and when?
Rutherford discovered protons in 1919
Who discovered neutrons and when?
It was discovered by James Chadwick in 1932.
What is a proton?
The proton is a subatomic particle with an electric charge of +1 elementary charge.
What is a neutron?
The neutron is a subatomic particle with no net electric charge and a mass slightly larger than that of a proton.
Where are protons and neutrons located in an atom?
Protons and neutrons are located in the nucleus of the atom, which is small. Most of the mass of the
atom is due to the nucleus.
Where are electrons located in an atom?
Electrons are located outside of the nucleus. Most of the volume of the atom is due to electrons.
What do atoms consist of?
The atom consists of positive, negative, and neutral entities (protons , electrons and neutrons ).
What is the electronic charge?
The quantity 1.602 x 10^(–19) C is called the electronic charge.
What is the charge of an electron?
The charge on an electron is –1.602 x 10^(–19) C
What is the charge of a proton?
the charge on a proton is +1.602 x 10^(–19) C
What is the charge of a neutron?
neutrons are uncharged.
What is the electric charge of an atom?
Atoms have an equal number of protons and electrons thus they have no net electrical charge.
What is an atomic mass unit?
is a unit of mass used to express atomic and molecular masses. It is the approximate mass of a hydrogen atom, a proton, or a neutron. (amu)
How much does one amu equal?
1 amu = 1.66054 x 10–24 g.
What is the mass of a proton?
The mass of a proton is 1.0073 amu
What is the mass of a neutron?
a neutron is 1.0087 amu
What is the mass of an electron?
and an electron is 5.486 x 10^(–4)
amu.
How much in an angstrom in meters?
1 Å = 1 x 10–10 m.
What is the radii of most atoms?
1 Å
How are atomic mass and atomic numbers written?
• Atomic number (Z) = number of protons in the nucleus.
• Mass number(A) = total number of nucleons in the nucleus (i.e., protons and neutrons).
• By convention, for element X, we write (z on the top left corner of X, and a on the bottom left corner of X)
What is an Isotope?
All atoms of a specific element have the same number of protons.
• Isotopes of a specific element differ in the number of neutrons.
What is a nuclide?
An atom of a specific isotope is called a nuclide.
• Examples: Nuclides of hydrogen include:
1H = hydrogen (protium), 2H = deuterium, 3H = tritium; tritium is radioactive.
What is atomic weight?
Atomic weight (AW) is also known as average atomic mass (atomic weight).
• Atomic weights are listed on the periodic table.
How is average atomic mass determined?
We average the masses of isotopes to give average atomic masses.
• Naturally occurring C consists of 98.93% 12C (12 amu) and 1.07% 13C (13.00335 amu).
• The average mass of C is:
• (0.9893)(12 amu) + (0.0107)(13.00335 amu) = 12.01 amu.
Where are the atomic weights of elements listed?
Atomic weights are listed on the periodic table.
What is a mass spectrometer?
A mass spectrometer is an instrument that allows for direct and accurate determination of atomic
(and molecular) weights.
How does a mass spectrometer work?
• The sample is charged as soon as it enters the spectrometer.
• The charged sample is accelerated using an applied voltage.
• The ions are then passed into an evacuated tube and through a magnetic field.
• The magnetic field causes the ions to be deflected by different amounts depending on their mass.
• The ions are then detected.
• A graph of signal intensity vs. mass of the ion is called a mass spectrum.
What is the periodic table?
The periodic table is used to organize the elements in a meaningful way.
What are the rows in the periodic table called?
Rows in the periodic table are called periods.
What are columns in the periodic table called?
Columns in the periodic table are called groups.
What are the elements in Group 1A called?
alkali metals
What are the elements in Group 2A called?
alkaline earth metals
What are the elements in Group 6A called?
Chalcogens
What are the elements in Group 7A called?
halogens
What are the elements in Group 8A called?
noble gases
Where are Metallic elements or metals located?
Metallic elements , or metals, are located on the left-hand side of the periodic table (most of the
elements are metals).
What are the qualities of metals?
Metals tend to be malleable, ductile, and lustrous and are good thermal and electrical conductors.
Where are Nonmetallic elements , or nonmetals located?
Nonmetallic elements , or nonmetals, are located in the top right-hand side of the periodic table.
What are the qualities of nonmetals?
Nonmetals tend to be brittle as solids, dull in appearance, and do not conduct heat or electricity
well.
What are metalloids and where are they located?
Elements with properties similar to both metals and nonmetals are called metalloids and are located
at the interface between the metals and nonmetals.
Which elements are metalloids?
B, Si, Ge, As, Sb and Te.
What is a molecule?
A molecule consists of two or more atoms bound tightly together.
What is a chemical formula
The chemical formula indicates
1. which atoms are found in the molecule, and
2. in what proportion they are found.
What is a molecule made up of two atoms called?
diatomic molecule
What are allotropes?
Different forms of an element, which have different chemical formulas, are known as allotropes. Allotropes differ in their chemical and physical properties.
What are molecular compounds?
Compounds composed of molecules are molecular compounds.
• These contain at least two types of atoms.
• Most molecular substances contain only nonmetals.
What are Molecular formulas?
These formulas give the actual numbers and types of atoms in a molecule.
• Examples: H2O, CO2, CO, CH4, H2O2, O2, O3, and C2H4.
What are Empirical formulas?
• These formulas give the relative numbers and types of atoms in a molecule (they give the lowest
whole-number ratio of atoms in a molecule).
• Examples: H2O, CO2, CO, CH4, HO, CH2.
What is structural formula?
The structural formula gives the connectivity between individual atoms in the molecule.
What are perspective drawings?
Perspective drawings use dashed lines and wedges to represent bonds receding and emerging
from the plane of the paper.
What are Ball-and-stick models?
Ball-and-stick models show atoms as contracted spheres and the bonds as sticks.
• The angles in the ball-and-stick model are accurate.
What are Space-filling models?
Space-filling models give an accurate representation of the 3-D shape of the molecule.
What is an ion?
If electrons are added to or removed from a neutral atom, an ion is formed.
What is a cation?
When an atom or molecule loses electrons it becomes positively charged.
• Positively charged ions are called cations .
What is an anion?
When an atom or molecule gains electrons it becomes negatively charged.
• Negatively charged ions are called anions .
What type of ions do metals generally tend to be?
cations
What type of ions do non-metals tend to be?
anions
What are polyatomic ions?
When molecules lose electrons, polyatomic ions are formed (e.g. SO 4
2–, NO3
–).
Important info on Predicting Ionic Charges!
• An atom or molecule can lose more than one electron.
• Many atoms gain or lose enough electrons to have the same number of electrons as the nearest noble
gas (group 8A).
• The number of electrons an atom loses is related to its position on the periodic table.
How are ionic compounds formed?
• To form NaCl, the neutral sodium atom, Na, must lose an electron to become a cation: Na+.
• The electron cannot be lost entirely, so it is transferred to a chlorine atom, Cl, which then
becomes an anion: Cl–.
• The Na+ and Cl– ions are attracted to form an ionic NaCl lattice, which crystallizes.
What is an ionic compound?
NaCl is an example of an ionic compound consisting of positively charged cations and negatively
charged anions.
What is the difference between an ionic compound and a molecular compound?
In general, ionic compounds are combinations of metals and nonmetals, whereas molecular
compounds are composed of nonmetals only.
How do write empirical formulas for ionic compounds?
• You need to know the ions of which it is composed.
• The formula must reflect the electrical neutrality of the compound.
• You must combine cations and anions in a ratio so that the total positive charge is equal to the
total negative charge.
• Example: Consider the formation of Mg3N2:
• Mg loses two electrons to become Mg2+
• Nitrogen gains three electrons to become N3–.
• For a neutral species, the number of electrons lost and gained must be equal.
• However, Mg can only lose electrons in twos and N can only accept electrons in threes.
• Therefore, Mg needs to lose six electrons (2x3) and N gains those six electrons (3x2).
• That is, 3Mg atoms need to form 3Mg2+ ions (total 3x2 positive charges) and 2N atoms need
to form 2N3– ions (total 2x3 negative charges).
• Therefore, the formula is Mg3N2.
How many elements are required for life?
only about 29 are required for life
What percent of cells in water?
Water accounts for at least 70% of the mass of most cells
What is the most common element in the solid components of cells?
Carbon is the most common element in the solid components of cells.
What are the most important elements for life?
The most important elements for life are H, C, N, O, P and S
What are the most important ions for life?
Na+, Mg 2+, K+, Ca 2+, and Cl–
What are trace elements?
other required 18 elements are only needed in trace amounts
What is Chemical nomenclature?
Chemical nomenclature is the naming of substances
What are Common names?
are traditional names for substances (e.g., water, ammonia).
What are Systematic names?
Systematic names are based on a systematic set of rules.
• Divided into organic compounds (those containing C, usually in combination with H, O, N, or S)
and inorganic compounds (all other compounds).
What are monoatomic ions?
Ions formed from a single atom are called monoatomic ions.
How are cations named?
• Cations formed from a metal have the same name as the metal.
• Example: Na+ = sodium ion.
• Ions formed from a single atom are called monoatomic ions.
• Many transition metals exhibit variable charge.
• If the metal can form more than one cation, then the charge is indicated in parentheses in the
name.
• Examples: Cu+ = copper(I) ion; Cu2+ = copper(II) ion.
• An alternative nomenclature method uses the endings -ous and -ic to represent the lower and
higher charged ions, respectively.
• Examples: Cu+ = cuprous ion; Cu2+ = cupric ion.
• Cations formed from nonmetals end in -ium.
• Examples: NH4+ = ammonium ion; H3O+ = hydronium ion.
What is the suffix for Monatomic anions
• Monatomic anions (with only one atom) use the ending -ide .
• Example: Cl– is the chloride ion.
Give examples of Some polyatomic anions that also use the -ide ending
Some polyatomic anions also use the -ide ending:
• Examples: hydroxide, cyanide, and peroxide ions.
What are oxyanions.?
Polyatomic anions (with many atoms) containing oxygen are called oxyanions.
• Their names end in -ate or -ite. (The one with more oxygen is called -ate.)
• Examples: NO3
– is nitrate; NO2
– is nitrite.
Polyatomic anions containing oxygen with more than two members in the series are named as follows
(in order of decreasing oxygen):
• per-….-ate example: ClO4 – perchlorate
• -ate ClO3 – chlorate
• -ite ClO2 – chlorite
• hypo-….-ite ClO– hypochlorite
How do you name acids?
• 1. Anion-ide
– Hydro-Anion-ic acid
• 2. Anion- ate
– Anion-ic acid
• 3. Anion-ite
– Anion-ous acid
How do you find the Names and Formulas of Binary Molecular Compounds?
• 1. The name of the element farthest to the left of the periodic table is usually
written first
• If both elements are in the same group in the periodic table the lower one is
named first
• The name of the second element ends in –ide
• Greek prefixes are used to indicate the # of atoms of each element. Mono is
never used with the first element. If the prefix ends in a or o and the name of
the second element begins with a vowel then the a or o is dropped
Name the groups of the periodic table
– Representative (A)
• Alkali (1A)
• Alkaline (2A)
• Chalcogens (6A)
• Halogens (7A)
• Noble gases (8A)
--Transition Metals (B)
• Metals
• Nonmetals
• Metalloids
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