Chapter 3 - Elements, Compounds and their Composition

NAMING ELEMENTS

element names come from many sources (Greek, Latin, German)

ATOMIC THEORY

John Dalton's theory regarding composition of an element

1. Matter is composed of small indivisible particles called ATOMS
2. Atoms of the same element are IDENTICAL
3. Compounds are composed of atoms of different elements combined in whole number ratios.
4. Chemical reactions are merely the REARRANGEMENT of atoms into different combinations

 COMPOUND - a substance that contains more than one element

Covalent Bond - the force that bonds two atoms together.

Molecule - a basic unit of two or more atoms held together by a covalent bond.

• An element is made up of a group of atoms
• A compound is made up of a group of molecules

Formula - a symbolic representation of a element or compound

Structural formula - arrangement of actual bonds

ELECTRICAL NATURE OF MATTER: IONS

Electrostatic forces - a force of attraction between opposite charges and a force of repulsion between like charges.

IONS - Atoms that are electrostaically charged

Cation - positively charged ions

Anions - negatively charged ions

Ionic Compounds - compounds that consist of ions

Ionic bond - the electrostatic force holding ions together.

Polyatomic ions- groups of atoms covalently bonded that is also an anion or cation

MODELS OF AN ATOM

Electrons - negatively charged subatomic particles

1. Thomson - Plum Pudding Model

2. Rutherford - small dense core containing positive charge (nucleus)

• Nucleus - small dense core containing positive charges
• nucleons - particles in the nucleus

1. protons - positively charged subatomic particles
2. neutrons - subatomic particle with no charge

ATOMIC NUMBER - the number of protons in the atoms nucleus (total positive charge)

MASS NUMBER - the number of protons and neutrons (nucleons) in the nucleus

# Electrons equals # protons in a neutral atom

ISOTOPE - atoms having the same atomic number but different mass numbers

Write an Isotope in the order:

Copper:

Both have 20 PROTONS, but # neutrons is different (34 and 36, respectively)

STANDARD MASS

all isotopes compared to mass of 12C = EXACTLY 12 atomic mass units (amu)

Atomic mass unit (amu) - is a mass of exactly 1/12 of the mass of 12C.