periodic tablec, trends, and bonding

isotopes

atoms of the same element which have different mass numbers due to the different numbers of neutrons in the nucleus

Relative atomic mass

the average of mass numbers of the isotopes of the element

as they occur naturally

taking their abundances into account and expressed on a scale in which the atoms of carbon-12 isotope have a mass of exactly 12 mm.

relative atomic mass exam def

average mass of atoms of element compared to 1/12 mass of carbon-12 isotope

aufbau principle

when building up electron configuration of an atom in its ground state, the electrons occupy the lowest energy levels

hunds rule of maximum multiplicity

when there are 2 or more orbitals of the equal energy available, the electrons occupy them singly before filling them in pairs

pauli exclusion principle

no more than 2 electrons may occupy an orbital and they must have an opposite spin

atomic radii

half the distance between the nuclei of two atoms of the same element joined together by a single covalent bond

electronegativity

the relative attraction that an atom in a molecule has for the shared pair of electrons in a covalent bond

diatomic elements

pure elements that exist as molecules

octet rule

when bonding occurs, electrons tend to reach the electron configuration of 8 electrons in the outermost energy level

valency

the number of atoms of hydrogen or any other monovalent element with which each atom of the elements combines

valence shell

outermost energy level

valence electrons

number of electrons in valence shell

ionic bonding

the force of attraction between oppositely charged ions

crystal lattice

three-dimensional arrangement of ions

polyatomic ions

ions which contain 2 or more elements

covalent bonding

the sharing of electrons

covalent bonding formation step 1

atomic orbitals start to overlap

covalent bond step 2

orbitals overlap, there will be a point where one hydrogen atom will be just as attracted to the positive nucleus from the other hydrogen atom as it is to its own nucleus.

covalent bond step 3

the positively charged nuclei of hydrogen are attracted to the increased electron density between them, pulling them closer together

covalent bond step4

orbitals start to overlap and merge creating a region called the bonding or molecular orbital, the covalent bond

double covalent bond

2 pairs of electrons shared between 2 atoms

triple covalent bond

when 3 pairs of electrons are shared

valence bond theory

chemical bonds are formed from overlapping of atomic orbitals of different atoms, which forms a molecular orbital

sigma bonds

head on overlap of atomic orbitals

pi bonds

formed from sideways overlap of p orbitals

a polar covalent bond

unequal sharing of the pair of electrons

a pure covalent bond

equal sharing of electrons