Chemistry Unit 1 Keyterms

Atomic Radius

distance between the nucleus and surrounding shells

Effective Nuclear charge

positive charge that pulls electrons towards the nucleus

Electronegativity

tendency of an atom to attract electrons

Ionization energy

amount of energy needed to remove an electron from an isolated atom or molecule

Electron affinity

energy change that occurs by adding an electron to a gaseous atom

Ionic

atoms or molecules that carry a positive or negative charge because they have gained or lost electrons.

Molecular

anything related to molecules, which are groups of two or more atoms bonded together

Lone pair

a pair of valence electrons that are not involved in chemical bonding

Valence electron

Electrons that are in the furthest electron cell of an atom

Octet rule

The rule that states that atoms tend to gain, lose, or share electrons to achieve a stable configuration of eight electrons in their valence shell

Isotope

variations of chemical elements that have the same amount of protons but different amounts of neutrons

Isotopic abundance

how much of each type of isotope an element has in nature

Dalton’s atomic theory

• All matter is made up of tiny, indivisible particles called atoms

• All atoms of an element are identical 

• Atoms of different elements are different

• Atoms are rearranged to form new substances in chemical reactions, but they are unable to be created or destroyed 

Thomson's Atomic Theory

All atoms contain negatively charged subatomic particles called electrons; pudding model

Rutherford’s Atomic Theory

Atoms have a nucleus surrounded by electrons called orbits

Bohr’s Atomic Theory:

Electrons move in fixed orbits that have fixed energy levels around the nucleus, and they can jump between these levels when energy is absorbed or emitted.