Atomic Structure and Periodic Table Flashcards
Why does chromium have a different electronic configuration?
in the case of chromium, the half-filled 3d and 3s sublevels make the atoms of chromium more stable.
What is the electronic configuration of bromine?
[Ar] 3d¹⁰ 4s² 4p⁵
Orbital definition
An orbital is a region within an atom that can hold up to two electrons of opposite spin.
Periodicity definition
A regularly repeating pattern of atomic, physical and chemical properties with increasing atomic number.
First ionisation energy definition
The energy required to remove one electron from
each atom in one mole of gaseous atoms to form one mole of gaseous 1+ ions
What is the first ionisation of magnesium
Mg (g) –> Mg+(g) + e-
Second ionisation energy definition
The energy required to remove one electron from each 1+ ion in one mole of gaseous ions to form one mole of gaseous 2+ ions
The 1st ionisation energy of potassium
K (g) –> K+ (g) + e-
The overall trend for an ionisation energy across is a period is …… because …….
- increases
- nuclear charge increases
shielding stays roughly the same
atomic radius decreases slightly
The overall trend for an ionisation energy down a group is ….. because……
- decreases
-nuclear charge increases a lot
-shell number increases
-shielding increases
-atomic radius increases - shielding outweighs nuclear charge
Explain why the 1st ionisation energy of sulfur is lower than that of chlorine (2 marks)
- outer electron is removed from same sub shell
- sulfur nuclear charge is 1 less than chlorine
What is Hund’s rule?
- that electrons will occupy the orbitals singly before pairing takes places within every sub shell
What is the Pauli Exclusion Principle?
- that two electrons cannot occupy the same orbital unless they have opposite spins.
- electron spin is shown by the use of upward and downward arrows.
Who discovered the electron?
JJ Thompson
Who discovered the proton?
Ernest Rutherford
Who discovered the neutron?
James Chadwick
What evidence do we have to know that quantum shells exist?
- successive ionisation energies
- emission spectra
where can electron-electron repulsion occur? (sheilding)
- between adjacent quantum shells
- between two electrons in the same orbital
- between electrons in different orbitals within a given quantum shell
How does atomic radii change across period 2/3?
- atomic radii decreases across the group
- because atomic number increases, and therefore the nuclear charge
- this leads to an increase in attractive force (electrostatic) between the nucleus and outer electrons
Definition of relative atomic mass Ar
the average mass of an atom of an element (taking into account the relative abundances of isotopes) compared to one twelfth of the mass of one atom of carbon-12
Definition of relative isotopic mass
the mass of an atom of an isotope compared to one twelfth of the mass of one atom of carbon-12.
What are nucleons
the sub-atomic particles that exist in the nucleus of atoms (protons & neutrons).
What are strong nuclear forces
forces that hold together protons & neutrons in the nucleus.
What are isotopes
atoms of the same element with different numbers of neutrons. (same numbers of protons and electrons)
What is the atomic number of an element showing
the number of protons in the nucleus of an atom of that element
What is a species in chemistry
a substance composed of chemically identical entities
What is the relative molecular mass
a compound is the sum of the relative atomic masses of all the atoms in a molecule compared to one twelfth of the mass of one atom of carbon-12.
What is relative formula mass
the sum of the relative atomic masses of all the atoms in the formula compared to one twelfth of the mass of one atom of carbon-12.
What successive ionisation energy
the energy required to remove the electrons one after the other.
Outline the steps of mass spectronometry
Vaporisation
Ionisation (using an electron gun)
Acceleration
Deflection (by an electromagnet)
Detection (negatively charged detection plate)
How can Ar be calculated form an emission spectra from a mass spectrometer
(m/z x abundance) / total abundance
What is the shape of an s orbital
Spherical
What is the shape of a p orbital
dumbbell
How many electrons can a p orbital contain
6
How many electrons can an s orbital contain
2
How many electrons can a d orbital contain
10
How does atomic radius change DOWN a group
Increases
How does atomic radius change across a period
Decreases
How does first ionisation change across a period
Increasing along the period. This is due to a decreasing atomic radius with the exception and increasing nuclear charge so outer electrons are held on more strongly (higher electrostatic attractions)
This is with the exception of group 3 and group 6 elements, which cause small decreases. This is due to the electron configurations containing an unpaired electron that requires less energy to remove, resulting in smaller ionisation energy and small dips in the general increase
How does bonding and structure change across period 3
Na, Mg and Al are all metals with metallic bonding, with electrostatic forces increase from Na to Al
Si is a giant covalent structure with strong covalent binds that require a lot of energy to break
P, S and Cl2 are all simple covalent molecules with London forces, which are weak and relatively easy to overcome
Ar is a noble gas that exists on its own, making it very stable and unreactive.
