chem unit 1 pt 9

chemistry

happens as atomes join in chemical bonds

1. represented by chemical formulas

2. the subscript to the right of the symbol of an element tells the number of atoms of that element in one molecule of the compound

empirical formulas

give the lowest whole-number ratio of atoms of each element in a compound

ex. CH

molecular formulas

give the actual number of atoms of each element in a compound

1. if we have the ____ of a compound, we can determine it’s empirical formula. The reverse is not true without more information

ex. CH C2H2 C6H6

chemical bonds

always involve the sharing of electrons between 2 or more nuclei

three types

1. covalent or molecular compounds

2. ionic compounds

3. metallic systems

they are loosely defined by the way electrons are “shared” between the constituent atoms

ion

an atom that gains or loses electrons

1. cations (+)

2. anions (-)

cation

formed when 1 or more electrons are lost

1. positive (more protons than electrons)

anion

formed when 1 or more electron is gained

1. negative (more electrons than protons)

ionic charge

shown by a superscript to the right of the atomic symbol

ex. Ca²+ (Ca^2+)

polyatomic ions

formed from compounded atoms gaining or losing 1 or more electrons

ex. polyatomic cation - 4(NH^+)

covalent compounds

electrons are close to evenly shared between 2 atoms that are bonded

1. X represents an electron “from” hydrogen

2. circle represents an electron “from” carbon

ionic compounds

are generally formed between metals and nonmetals

1. electrons are transferred from the metal to the nonmetal

2. the oppositely charged ions attract each other

3. only empirical formulas are written

ex. NaCl

metals

good conductors because some electrons are shared across many nuclei

1. kind of like large scale plum pudding