2023 CHM CHAPTER 2

Electronegativity of an atom is

• to measure the ability of an atom to attract a bonding pair of electron in covalent bond

• the more inclined atom is to lose electron, the more likely that atom will pull electron towards itself

• to measure the ability of an atom to donate a bonding pair of electron in covalent bond

• increasing down a group

Electron affinity, EA is

• energy change that occurs when 1 mol of electron is accepted by 1 mol of atom in its gaseous state to form a cation

• energy change that occurs when 1 mol of electron is accepted by 1 mol of atom in its gaseous state to form an anion

• energy change that occurs when 1 mol of electron is accepted by 1 mol of atom in its solid state to form an anion

• energy change that occurs when 1 mol of proton is accepted by 1 mol of atom in its gaseous state to form an anion

Aufbau principle

• No two electrons in an atom may have the same set of four quantum numbers ( n, l, ml, ms )

• Each orbital should contain a maximum of 2 electrons which must have to be opposite spin.

• Set of orbitals of the same energy level which is the degenerate level, the electron occupy the orbital singly with parallel spin before they occupy in pair.

• Electrons occupy orbital in the order of increasing energy levels.

Hund's Rule

• Electrons occupy orbital in the order of increasing energy levels.

• Set of orbitals of the same energy level which is the degenerate level, the electron occupy the orbital singly with parallel spin before they occupy in pair.

• No two electrons in an atom may have the same set of four quantum numbers ( n, l, ml, ms )

• Each orbital should contain a maximum of 2 electrons which must have opposite spin.

Pauli's Exclusion Principle

• No two electrons in an atom may have the same set of four quantum numbers ( n, l, ml, ms )

• Set of orbitals of the same energy level which is the degenerate level, the electron occupy the orbital singly with parallel spin before they occupy in pair.

• Electrons occupy orbital in the order of increasing energy levels

• Each orbital must contain a maximum of 2 electrons which must have opposite spin.

Choose FALSE statement regarding Electronegativity.

• The strength of electronegativity increases across a period in the periodic table because the effective nuclear charge zeff increases.

• The strength of electronegativity decreases down a group in the periodic table because the principal quantum number increases.

• The ability of an atom to attract a bonding pair of electrons in ionic bond.

• Ionic bond will be formed between atoms with AEN > 2.0.

What is isoelectronic?

• chemical species having the same number of electron, hence the same ground-state electron configuration.

• chemical type having the same number of proton, hence the same electron number

• chemical species having the different number of electron, thus the different proton number.

• chemical species having the same number of proton, hence the same ground-state electron configuration.

First ionization energy is

• minimum energy required to attract 1 mol of electrons to a valence shell of 1 mol of atom in its ground state

• minimum energy required to remove 1 mol of electrons in a valence shell of 1 mol of atom

• minimum energy required to remove 1 mol of electrons in a valence shell of 1 mol of gaseous atom in its ground state

• minimum energy required to attract 1 mol of electrons to a valence shell of 1 mol of gaseous atom in its ground state

Select the TRUE regarding ionization energy

• Atoms with low IE form cations

• Atoms with high IE form cations

• IE increases down a group

• IE increases across a period

HOW anomalies in First IE trends in Period 2 happen?

• occur due to stability of electron configuration

• The increase in the 1st IE is not uniform

• The electron in Be is removed from a fully filled 2s orbital that is stable

• The electron in B is removed from a fully filled 2s orbital that is stable

Answer explanation

General Statement :

1. > First IE should increase across the period.

2. > Occur due to stability of electron configuration

; Be has higher first IE than B even when Be is placed before B.

• This is due to Be that has 4 electrons, in which has electron configuration of :
  1s² 2s²

Hence the electron in Be is removed from a fully filled 2s orbital.

Fully filled configuration is more stable, increasing the energy to remove the electron.