Explanation:
To solve this problem, we simply use the periodic table of elements which groups elements based on their atomic numbers.
The atomic number of an element is the number of protons it contains. The protons are the positively charged particles within an atom.
- The vertical arrangement of elements on the periodic table is the group.
- The horizontal arrangement of elements is the period.
Now;
Noble gases belongs to group 18
Alkali earth metals belongs to group 2
Halogens belongs to group 17
Alkali metals belongs to group 1
Transition metals belongs to group 3-12
Answer:
3 elements
Calcium,oxygen and hydrogen
Pressure caused by high temperatures are balanced by gravity
The first word could be: pairs and the second: relax
