Trends in the Periodic Table Flashcards
What is the atomic radius?
Half the distance between the nuclei of two atoms of the same element that are joined together by a single covalent bond.
What are the trends of atomic radii?
Atomic radii increase down a group:
- New energy level
- Screening effect of inner electrons
Atomic radii decrease across a period:
- Increase in effective nuclear charge
- No increase in screening effect.
What is the first ionisation energy?
The minimum energy required to completely remove the most loosely bound electron from a neutral gaseous atom in its ground state.
What is the second ionisation energy?
Minimum amount of energy required to remove the second most loosely bound electron from a positive ion formed when the first electron was removed.
What are the trends of ionisation energy?
Ionisation energy decreases down a group:
- Increasing atomic radii
- Screening effect of inner electrons
Ionisation energy increases across a period:
- Decreasing atomic radii
- Increasing effective nuclear charge.
What are the exceptions to the general trend across a period?
The irregularities are explained by the fact that any sublevel that is completely filled or exactly half filled is more stable. The first ionisation energies are higher than expected since it requires more energy than expected to break up these stable arrangements by removing an electron.
What is the formula for ionisation energies?
K(g) —> K^+ + e^-
g stands for gaseous.
this is for first ionisation energy.
K^+ —-> K^2+ +e^-
Second ionisation energy.
(See book for more) pg. 87
Why is the second ionisation energy always higher than the first?
As the second electron is being removed from a positively charged electron, which is smaller than a neutral atom, which means that the electrons are closer to the nucleus and the positive charge. Causing it to require more enegy to remove the second electron.
What is the trend in electronegativity?
Decrease down groups:
- Increasing atomic radius
- Screening effect of inner electrons.
Increase across periods
- Increasing effective nuclear charge
- Decreasing atomic radius
What is the trend in with alkali metals(group1)?
Increasing reactivity as you go down the group.
What is the trends within halogens (group 7)?
Decreasing reactivity as you go down the group.
Why do the boiling points and melting points of the noble gases(group 8) increase?
Due to stronger Van Der Waal forces.
