Unit 1 - Periodicity Flashcards
Why are Noble Gases stable?
They have full outer energy levels, containing 8 electrons.
Elements in the same ______ of the periodic table are said to have _______ chemical properties since they react in a similar way. This is due to them having the same number of ______ _____.
- column
- similar
- outer electrons
What is the covalent radius?
A measure of the size of an atom. It is half the distance between the nuclei of two covalently bonded atoms of the element.
What happens to the covalent radius going across a period?
The covalent radius decreases.
What happens to the covalent radius going down a group?
The covalent radius increases.
Why does the covalent radius decrease going across a period?
Going across a period, the number of energy levels remains constant. The number of protons increases which increases the nuclear charge (the force pulling electrons towards the nucleus). Stronger nuclear charge = smaller atom/nuclear radius.
Why does the covalent radius increase going down a group?
Going down a group, the elements have **additional inner energy levels* occupied by electrons. The covalent radius increases because each energy level shields the outer electrons from the positive nucleus. This results in the size of the atom getting larger as the electrons aren’t as strongly pulled toward the nucleus. Although nuclear charge also increases, its effect is outweighed by the much greater radius of each additional energy level.
What is ionisation energy?
The energy required to remove one mole of electrons from one mole of gaseous atoms.
In ionisation energy, what is always the state symbol?
Gas (g)
What happens to the first ionisation energy going across a period?
It increases.
Why does the first ionisation energy increase going across a period?
There is increased nuclear charge meaning the atoms are smaller resulting in a greater attraction for the outer electrons. **More energy is required to overcome this
** therefore there is an increase in 1st ionisation energy.
What happens to the first ionisation energy going down a group?
It decreases.
Why does the first ionisation energy decrease going down a group?
Going down a group, there is an increased shielding of the nuclear charge by the extra occupied energy levels meaning the atoms are larger. There is less attraction from the nucleus to outer electrons so less energy is required to overcome the attraction therefore there is a decrease in 1st ionisation energy.
Why is the second ionisation energy of Lithium (2,1) substantially larger than the first?
The second electron to be removed from lithium is removed from a new energy level,closer to the nucleus compared with the first electron which is removed from the other energy level which is further from the nucleus. The second electron is therefore more strongly attracted to the nucleus as it is closer and experienced agreater force of attraction, requiring more energy to break.
What is electronegativity?
A measure of the attraction that an atom has for bonded electrons.
The higher the _______ value for an element the _______ its attraction for ______.
- electronegativity
- stronger
- electrons
What group of elements do not have an electronegativity value? Why?
Noble gases. They do not have electronegativity values as they are unreactive. They do not form bonds so do not need to attract electrons.
What happens to the electronegativity values going across a period? ➡️
It increases.
What happens to the electronegativity values going down a group? ⬇️
They decrease.
