Chemistry- Atomic structure

atomic number

number of protons in a nucleus of an atom, will determine position on periodic table

proton number

is same as atomic number

mass number

total number of protons and neutrons in nucleus of atom

nucleon number

same as mass number

what is the trend in atomic radius across and down group and why

increases down group due to adding shells and shielding

what is the trend for atomic radius across a period

decreases across a period because more electrons are being added to same shell, positive nucleus is pulling shell inwards with the increasing nuclear charge across period

trend for ionic radius down a group

same trend as atomic radius

trend for ionic radius across a period

corresponds with the charge of the group, the more negative, the bigger, positive = smaller

define isotope

atoms of the same element with the same number number of protons but different number of neutrons

define atomic orbital

region of space where there is a high probability of finding an electron

define the term principle quantum number

an electron's main energy level or shell in an atom, indicating its distance from the nucleus and the orbital's size

define electron configuration

a way of representing the arrangement of the electrons in atoms showing the principal quantum shells, sub shells and number of electrons present

spin-pair repulsion

a pair of electrons in the same orbital repel each other because of same charge, spinning in opposite directions reduces the repulsion

what is hund’s rule

Every orbital in a sub-shell is single occupied before
any orbital is doubly occupied

what is the aufbau principle

electrons will fill lowest available orbital to help atom achieve its ground state