What is diagonal relationship? Why does `Li` resemble with `Mg`?

Why does Be resemble Al?

What is called diagonal relationship ?

What is diagonal relationship? Give one example.

What is diagonal relationship? Give one example.

Li shows diagonal relationship with

What is meant by 'diagonal relationship'? Why do some elements show diagonal relationship? How does lithium resemble magnesium in its chemical behaviour?

Be resembles Mg why ?

Li shows the diagonal relationship with

What do you mean by diagonal relationship?