E.S. Unit 2

The combined number of protons and neutrons is the .

• Atomic Number
• Mass Number

An represents the area in an atom where an electron is most likely to be found.

• Energy Level
• Isotope

is the attraction of two atoms for a shared pair of electrons that holds the atoms together.

• Ionic Bond
• Covalent Bond

An atom that gains or loses an electron is a charged particle called .

• Ion
• Molecule

is a substance that cannot be broken down into simpler substances.

• Compound
• Element

A tiny particle that has mass and a positive electrical charge is a .

• Proton
• Neutron

are solutions characterized by the formation of hydroxide ions (OH-).

• Acids
• Bases

The process of changing from a liquid into a gas is called .

• Sublimation
• Evaporation

The basic building blocks of matter are

• Molecules
• Compounds
• Atoms
• Elements

The nucleus of an atom is made up of

• Protons, Neutrons, & Electrons
• Electrons & Neutrons
• Protons & Neutrons
• Protons & Electons