Chapter 1-Electronic Configuration Flashcards
(19 cards)
How are electrons arranged in atoms?
Electrons are arranged in fixed energy levels called shells?
Note: Shells are orbits followed by electrons around an atoms nucleus.
What is each shell described by and what does that description tell us?
Each shell is described by a principal quantum number and it tells us the size of the shell.
What are the four subshells.
S, P, d, f
Each subshells contains one or more orbitals that can hold a certain number of electrons
Define: Orbital
Region in space where there is a maximum probability of finding an electron.
What is Aufbau Principle?
A method of showing of how atomic orbitals are filled in a definite order to give lowest energy arrangement.
Why do we fill the i.e. 4s orbital first instead of the 3d orbital?
Energy difference between 4s and 3d is very small therefore, an electron from 4s orbital can be promoted to half-fill or full-fill 3d orbital to make orbital more stable.
Define: Nuclear Charge
Number of protons or +ve charge in the nucleus
Define: Atomic Radius
Distance from the centre of the nucleus to the outermost orbit.
Define: Screening/Shielding Effect
The inner shells of electrons repel outermost electron this screening or shielding the from the attractive +ve nucleus.
Note: the outer electrons are loosely held by the nucleus.
List the 3 factors affecting atomic radius.
- Principal Quantum no.> Greater the no. of shells, greater radius
- Nuclear Charge>Greater the nuclear charge, smaller radius
- Screening Effect>Greater the screening, greater the radius
Trends in atomic radius of elements:
What happens to atomic radius as you go across a period?
The atomic radius generally decreases because:
- principal quantum no. remains the same,
- no. of protons increases,
- effective nuclear charge increases,
- attraction between protons and electron increases
hence atomic radius decreases
What happens to the atomic radius as you go down a group?
As you go down a group, atomic radius increases because:
- no. of electron increases
- no. of shells increases
- Screening effect increases
hence atomic radius increases
Trends in ionic radius of ions
What is the ionic radius of a positive ion compared to its atomic radius?
Smaller ionic radius compared to atomic radius:
- no. of electrons decreases
- shell no. decreases
- screening effect decreases
- effective nuclear charge increases
hence ionic radius is smaller
What is the ionic radius of a negative ion compared to its atomic radius?
Larger ionic radius compared to atomic radius because:
- no. of electrons increases
- increased repulsion/screening effect
- effective nuclear charge decreases
- electrons are held more loosely by nucleus
hence why bigger ionic radius than atomic
Define: Ionization Energy/I.E. (kJ/mol)
Is the energy needed to remove one electron from each atom of one mile of gaseous neutral atom to form one mile of unipositive ion.
(1st Ionization Energy)
Note: this definition follows for 2nd I.E. except to form a dispositive ion, etc.
Why do successive ionization energies increas?
Because nuclear charge increases
What is electronic configuration?
The arrangement of electrons in an atom.
What are the factors influencing I.E.?
- Atomic Radius: greater atomic radius, attraction between protons and outermost electrons decreases>less I.E.
- Shielding Effect: greater shielding effect, looser hold on outer electrons>less I.E.
- Stable Configuration: from half-filled or full-filled orbitals>more I.E.
What is the trend in I.E.:
a) Down a group?
b) Across a period?
a) I.E. Decreases because: no. of shells increases, shielding effect increases.
b) I.E. Increases because: principal quantum no. is =, effective nuclear charge increases.
