2.1 The Nature of Matter Study Guide

atoms
basic units of matter

1,000,000 atoms=
1 centimeter

components of an atom
protons, neutrons, and electrons

protons
positive charge
located in the nucleus
relatively big

electrons
negative charge
Located around the nucleus
Relatively small (tiny!)
Fill levels around the nucleus (2-8-8 pattern)

neutrons
neutral charge
Located in nucleus
Relatively big

elements
are pure substances made of only one type of atom

periodic table
Organized collection of all known elements

element symbol
letter(s) assigned to represent the element

atomic number
number of protons in the atom

atomic mass
the average mass of all atoms of that type (calculated by rounding neutrons + protons)

nuclei
are unstable and they breakdown over time

Compounds
are substances formed by atoms of two or more elements joined together by chemical bonds.

Compounds can be expressed with formulas
(H2O, CO2)

Ionic bonds
One or more electron is transferred from one atom to the next

Ionic bonds Results in
ions

Ions
are atoms that have gained or lost electrons, so they carry a charge

Covalent bonds
One or more electrons are shared by two atoms

Both atoms share at least
one of their electrons with the other

when atoms are joined by covalent bonds they form
molecules (may be the same element)

covalent bonds are stronger than ionic bonds because of
sharing