Chapter 2

Front 1

Elements and Compound

Back 1

Elements cannot be broken down chemically to other substances. A compound contains two or more elements in a fixed ratio.

Front 2

Essentials Elements of Life

Back 2

Carbon, Oxygen, Hydrogen, and Nitrogen make up aprox 96% of living matter.

Front 3

Subatomic Particles

Back 3

An atom is the smallest unit of an element. An aim gas a nucleus made op of positively charged protons an uncharged neutrons, as well as surround ing cloud of negatively charged electrons.

Front 4

Atomic Number and Atomic Mass

Back 4

The number of electron in an electrically neutral atom equals the number of protons.

Front 5

Isotopes

Back 5

Most elements have two or more isotopes, different in neutron number and therefore mass. Some isotopes are unstable and give off particles and energy as radioactivity . Radioactive tracers help biologist monitor biological processes.

Front 6

The Energy Levels Of Electrons

Back 6

In an atom, electrons occupy specific energy levels, each of which can be be represented by an electron shell of that atom.

Front 7

Electron Configurations and Chemical Properties

Back 7

Electron configurations determines the chemical behaviour of an atom. Chemical behaviour depends on the number of an atom. Chemical behaviour depends on the number of valence electrons - electrons in the outermost shell. An atom with an incomplete valance shell in reactive.

Front 8

Electron Orbitals

Back 8

Electrons move within orbitals, three-dimensinal spaces with specific shapes located within each successive shell.

Front 9

Covalent Bonds

Back 9

Chemical bond form when atoms interact and complete their valance shells. A single covalent bond is the sharing of a pair of valance electrons by two atoms: double bonds are the sharing two pairs of electrons. Molecules consist of two or more covalently bonded atoms. Electrons of a polar covalent bond are pilled closer to the more electronegative atom. A covalent bond in non polar if both arms are the same and there for equally electronegative.

Front 10

Ionic Bonds

Back 10

Two atoms may differ so much in electronegativity that one or more electrons are actually transferred from one atom to the other. The reset us a negatively charged ion (anion) and a positively charge ion (cation). The attraction between two ions of opposite charge is called an ionic bond.

Front 11

Weak Chemical Bonds

Back 11

A hydrogen bond is a weak attraction between one electronegative atom and a hydrogen atom thetas covalently linked to another electronegative atom. Van der Waals interactions occur when transiently positive and negative regions are of molecules attract each other. Weak bonds reinforce the shapes of large molecule and help molecules adhere to each other.

Front 12

Molecular Shape and Function

Back 12

A molecule's shape is determined by the positions of its atom's valence orbitals. When covalent bond form, the s and p orbitals in the valence shell of an atom may combine to form to form four hybrid orbitals that extend to the corners of imaginary tetrahedrons; such orbitals are responsible for the shapes go H₂O, CH₄, and many more complex biological molecules. Shape is usually the basis for the recognition of one biological molecule by another.

Front 13

2.4 without heading

Back 13

Chemical reactions change reactants into products while conserving matter. Most chemical reactions are reversible. Chemical equilibrium is reached when the forward and reverse reaction rates are equal.

Front 14

concept 2.1

Back 14

Matter consist of chemical elements in pure form and in combinations called compounds .

Front 15

Concept 2.2

Back 15

An element's properties depends on the structure of its atoms.

Front 16

Concept 2.3

Back 16

The formation and function of molecules depend on chemical bonding between atoms.

Front 17

Concept 2.4

Back 17

Chemical reactions make and break chemical bonds.