MATTER Anything that occupies space has mass MASS

MATTER: Anything that occupies space & has mass MASS: Quantity of matter an object has ELEMENTS: Substances composed of only one type of atom (Periodic Table)

• >90% biological mass from 4 elements 1. Carbon (C) 2. Hydrogen 3. Oxygen (O) 4. Nitrogen (H) (N)

ATOMS: Simplest particles of an element that can retain all properties of that element

STRUCTURE OF AN ATOM Nucleus: Central core; contains 2 kinds of particles • Protons: +ve charge • (# protons = atomic #) • Neutrons: no charge Electrons: surround nucleus (-ve charge) • Travel in energy levels (e- cloud) • 1 st energy level = 2 e • 2 nd energy level = 8 e-

• Energy Level Diagram Rules: Fill shells closest to the nucleus first. Up to 2 in the first shell, and up to 8 in the rest. 1. Carbon (C) 2. Hydrogen (H) 3. Oxygen (O) 4. Nitrogen (N)

Atoms have an equal # of electrons & protons = NO CHARGE

COMPOUNDS: Substances made of 2 or more elements; proportions fixed Ex: water (H 2 O)

Bonding • 2 Types: Covalent & Ionic • Form Molecules & Compounds: The simplest parts of substance that retain properties & can exist in free state

Bond formation during chemical reactions • COVALENT BOND: Forms when 2 atoms share e. Ex: O 2

Covalent Bonding http: //www. tutorvista. com/content/chemistry-iii/chemical-bonding/covalent-bonding-animation. php

• IONIC BOND: Forms by electrical attraction between 2 oppositely charged ions that are created by the transfer of electrons. Ion: Atom or compound w/charge Ex: Na. Cl

Ionic Bonding