Answer:
Barium
Explanation:
-Atomic #56
-5th element inn group 2
- soft
- silvery alkaline earth metal
Si has 4 available elections. Each Cl has 7.
7 x 4 = 28 + the 4 from your Si gives the total of 32 total electrons.
Answer:

Explanation:
The unbalanced nuclear equation is

Let's write X as a nuclear symbol.

The main point to remember in balancing nuclear equations is that the sums of the superscripts and of the subscripts must be the same on each side of the reaction arrow.
Then
235 = 4 + A , so A = 235 - 4 = 231, and
92 = 2 + Z , so Z = 92 - 2 = 90
And your nuclear equation becomes

Element 90 is thorium, so

2KClO₃ → 2KCl + 3O₂
mole ratio of KClO₃ to O₂ is 2 : 3
∴ if moles of O₂ = 5 mol
then moles of KClO₃ =

= 3.33 mol
Mass of KClO₃ needed = mol of KClO₃ × molar mass of KClO₃
= 3.33 mol × ((39 × 1) + (35.5 × 1) + (16 × 3) g/mol
= 407.93 g
Is this prier to a lab you've done?