periodicity

Question 1

who developed the periodic table

Answer 1

Dmitri Mendeleev developed the modern periodic table in the 1800s. Although there have been changes since then the basic principle is the same.

Question 2

how is the periodic table arranged

Answer 2

The periodic table is arranged into periods and groups by atomic number

Question 3

what do all elements in a group have in common and what does it result in

Answer 3

All elements in a group have the same number of electrons in the outer shell and therefore similar properties.

Question 4

what happens to atomic radius across a period and why

Answer 4

Atomic radius decreases across a period

As the number of protons increases the positive charge of the nucleus increases meaning electrons get pulled closer making the atomic radius smaller.

The extra electrons that the elements gain across a period are added to the outer hell energy level, so they don’t really provide any extra shielding effect

Question 5

what happens to the melting points in period 2 trendwise and explain the differences

Answer 5

-Sodium , magnesium and aluminum:

Metals and their melting points increase across the period because the metallic bonds get stronger

Th metallic bonds get stronger due to an increase in change and an increase in delocalized electrons and a decreasing radius

Therefore the melting points increase

-Silicon:

Silicon has a macromolecular structure with strong covalent bonds that link all its atoms together

A lot of energy is needed to break these bonds, so silicon has a very high melting point

-Phosphorus, sulfur, chlorine and argon :

All molecular substances so their melting points depend on the strength of their van der walls forces

Van der walls forces are weak and easy to overcome which is why the melting points of these molecules are so low.

Sulfur is the biggest molecule with it coming as S8, so it has the highest melting point.

Argon has the lowest melting point as it is monoatomic as therefore has extremely weak van der walls

Question 6

what happens to first ionisation energy across a period and why

Answer 6

There is a general increase in first ionization energy across period 3

This is because of the increasing attraction between the outer shells electrons and the nucleus sue to the proton number increasing