Chemistry Unit 5

Aufbau’s Principle

each electron goes into the lowest energy level orbital available.

Pauli exclusion principle

states that each orbital can only hold two electrons and they must have opposite spin.

Hund’s rule

states that electrons will occupy orbitals of the same energy singly before they pair up.

s

2

d

10

p

6

f

14

Periodic Law

When elements are arranged by increasing atomic number, there is a periodic repetition of their chemical and physical properties.

Valence electrons

Valence electrons are the outermost electrons in an atom. They are always either s or p electrons. Electrons in the d or f orbitals are actually inside the valence electrons.

Ionization energy (PERIODIC TREND)

the minimum energy required to remove an electron from a neutral atom in its gaseous state. increases as you go from left to the right

Octet rule

It states that atoms tend to gain, lose, or share electrons in order to acquire a full set of eight valence electrons.

Metals

Shiny, malleable, ductile solids that are good conductors of heat and electricity.

Metalloids

Properties of both and have metallic appearance but are brittle and only fair conductors of electricity.

Group (in the periodic table) (PERIODIC TREND)

Elements in the same group have similar chemical behaviors because their valence electrons determine how they interact with other atoms. Same valence electrons, reactivity, and bonding trends.

Period (in the periodic table) (PERIODIC TREND)

A horizontal row on the periodic table, numbered 1 through 7. Atomin numbers are increasing.

Periodic trend

electronegativity

the tendency of an atom to attract electrons in a bond. Increases as you go to the right and flourine is the most electronegative element.

More than 3/4 if the elements in the periodic table are _____

metals

Group 1 (except hydrogen)

Alkali metals

Group 2

Alkaline earth metals

Group 3-12

Transition metals

Group 18

Noble gases

Group 17

Halogens

Excited State

When the electrons are filling higher energy shells before lower energy shells. Ex. [Ne] 3s² 3p⁴ 4s¹

Ground state

Electrons fill lowest available electron shells first, so normal electron configuration

Most of the elements in group 16-18 are ______

Nonmetals

Elements in the same group have the same

number of valence electrons

Which energy level of the period 4 transition elements is being filled iwth electrons

Third energy level

What is the trend in atomic radii as you move from left to right across a period?

Generally decreasesdue to increased nuclear charge, which pulls electrons closer.

atomic radii

Atomic radius is the distance from the nucleus to the outermost electron shell.

Atomic Radius and Ionic Radius

Decrease left to right and increase top to bottom.

periodic trends

predictable patterns in the properties of elements, such as atomic radius, ionization energy, electronegativity, and metallic character, that repeat as you move across periods (rows) and down groups (columns) of the periodic table

third principle energy level

single s, five d, three p; flower

second principle energy level

one s and three p; dumbell shape

fourth principle energy level

1 s, 3 p, 5d, 7f, like a pumpkin