Chapter 2.pdf - The Molecules of Life Chapter 2 Core...

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The Molecules of Life Chapter 2
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Core concepts 1.The atom is the fundamental unit of matter. 2.Atoms can combine to form molecules linked by chemical bonds. 3.Water is essential for life. 4.Carbon is the backbone of organic molecules. 5.Organic molecules include proteins, nucleic acids, carbohydrates, and lipids, each of which is built from simpler units. 6.Life likely originated on Earth through a set of chemical reactions that gave rise to the molecules of life.
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Living organisms are structurally and functionally very diverse These differences are due to the molecules that build them Inspite of the diversity of molecules and their functions The chemistry of life is based on a few types of molecules, these molecules are made up of just a few elements 2.1 PROPERTIES OF ATOMS THE ATOM IS THE FUNDAMENTAL UNIT OF MATTER
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Elements : Pure substances that can not be broken down further. Contain only one type of unique atom Elements known today 118 Natural Elements 94 Artificially created Elements 24 Element is indicated by its symbol, For example, Carbon (C), Hydrogen (H), Helium (He) What are elements?
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Nucleus (6 protons + 6 neutrons) Electron Proton Neutron Carbon atom e e e e e e e + + + + + + + Carbon Atom
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Elements are composed of atoms. Atoms consist of protons , neutrons , and electrons . Protons are part of atomic nucleus and are positively charged particles Neutrons are part of atomic nucleus and do not have any electrical charge Electrons move around the nucleus and are negatively charged particles Protons and Neutrons together form the atomic nucleus 2.1 PROPERTIES OF ATOMS
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CARBON ATOM The number of protons is the atomic number and specifies the atom as a particular element. Atomic number = Number of Protons (given in periodic table) For example, an atom with 6 protons is always a carbon atom. The number of protons and neutrons determine the atomic mass . Atomic mass = Mass of ( Protons + Neutrons ) Mass number = Number of( Protons + Neutrons ) Therefore, Number of neutrons = Mass number Atomic number
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Isotopes are atoms of the same elements that have same number of protons and different numbers of neutrons . For example, carbon has three isotopes : 6 protons and 6 neutrons , atomic mass 12 (99%) 6 protons and 7 neutrons , atomic mass 13 (1%) 6 protons and 8 neutrons , atomic mass 14 (very small fraction) Typically, an atom will have the same number of protons and electrons. However, an atom that has lost an electron would be a positively charged ion and One that has gained an electron would be a negatively charged ion. CARBON ATOM
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ORBITALS AND SHELLS
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CARBON ATOM Electrons move around the nucleus within orbitals defined regions of space where an electron is most of the time. The maximum number of electrons in any orbital is two.
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