Trends and periodic table Flashcards
Define atomic radius
It is half the distance between the nuclear of two atoms of the same element that are joined by a single covalent bond
Why does the value of the atomic radius decrease across a period?
The effect of the nuclear charge increases as there is more protons in the nucleus, but the amount of shell stays the same so the electrons are pulled closer to the nucleus
No increase in screening effect as all elements have the same outer amount energy level
What happens to the value of the atomic radius as you go down a group?
It increases
Why does the value of the atomic radius increases you go down a group?
Every time you go down you had an extra energy level further away from the nucleus
With extra energy levels, the screening effect of inner electrons reduces the pull of the positive nuclear charge on the outer electrons
What happens to the size of the atomic radius as you go across a period?
It decreases
Define ionisation energy
It is the minimum energy required to completely remove the most loosely bound electron from a neutral gaseous atom in the ground state
What happens to the value of the first ionisation energy as you go down a group?
It decreases
Why does the ionisation energy decrease down a group?
The atomic radius increases meaning the outermost electron gets further and further from the nucleus making it easier to remove
The increased screening effect of the inter electron makes the most loosely bound electron easier to remove
What happens to the value of the first ionisation energy as you go across a period?
It increases
Why does the first ionisation energy value increase across a period?
There is an increasing effect of nuclear charge so the most gross bound of electron gets pulled more strongly by the nucleus. Some more energy is needed to remove it.
The most loosely bound the electron gets closer to the nucleus as the atomic radius decreases
What are the exceptions to the first ionisation energy for the first 20 elements in the periodic table?
Beryllium and boron
Beryllium has a higher first ionisation energy than boron as it has a full outer shell, whereas boron has one electron in the two p shell, which is easier to remove
What would have a higher ionisation energy a half full shell or a shell with only one electron?
A full shell or a half shell have extra stability
Define second ionisation energy
It is the energy required to remove an electron from an ion with one positive charge in the gaseous state
What happens to the electronegativity value down a group?
It decreases
Why does the value of electronegativity decrease down a group
The atomic radius increases meaning that the atom has a weaker pull on electrons in a bond as they are further away
Screening effect of inner electrons increases which reduces the pool that the nucleus has an uouter electrons
What happens to the electronegativity value across the period?
It increases
Why does the electronegativity value increase across a period
Increased effect of nuclear charge
There is a decrease in atomic radius so the most loosely round electrons are closer to the nucleus so they have a stronger pole on it
What are the alkali metals?
They are group one meals
They are very reactive as they only have one electron in their outer energy level
Does the reactivity increase or decrease down alkali metals?
Increases
Why does the reactivity of alkali metals increased down a group?
You are an extra energy level further from the nucleus which increases the screening affect making the outer electrons easier to remove
By adding an extra energy level, we also increase the atomic radius reducing the point that the nuclear charge has the electrons
What what forms when alkali metals react with oxygen?
Deform oxides
Why are alkaline metal stored in oil?
As they easily react with oxygen in the air
They also lose their shiny colour when exposed to air
What happens to alkaline metals when they react with water?
They react vigourously
What forms when alkali metals react with water?
Hydrogen and hydroxideS
