Noble gas electron configurations are easier to write because they are shorter then full electron configurations. They Noble gas shortcut electron configuration is a way of summarizing the information about the electrons of an atom.
(this is what I used)
Answer:

Explanation:
We are asked to convert an amount in grams to moles. To do this, we use the molar mass. This is the number of grams in one mole of a substance. It is the same value numerically as the atomic mass on the Periodic Table, however the units are grams per mole, not atomic mass units.
Look up the molar masses for the individual elements.
- Sodium (Na): 22.9897693 g/mol
- Oxygen (O): 15.999 g/mol
Look back at the formula: Na₂O. Notice there is a subscript of 2 after sodium. This means there are 2 atoms of sodium in every molecule, so we have to multiply sodium's molar mass by 2 before adding oxygen's.
- Na₂O: 2(22.9897693 g/mol)+ 15.999 g/mol = 61.9785386 g/mol
Set up a ratio using the molar mass.

Multiply by the given number of grams.

Flip the ratio so the grams of sodium oxide can cancel each other out.




The original measurement of grams given has 3 significant figures, so our answer must have the same. For the number we calculated, that is the hundredth place.
The 4 in the thousandth place tells us to leave the 8.

There are <u>2.48 moles of sodium oxide</u> in 154 grams, so choice A is correct.
The reaction is;
2Na + 2H2O → 2NaOH + H2
Answer:
4.4 × 10^(23) atoms
Explanation:
The reaction is;
2Na + 2H2O → 2NaOH + H2
2 moles of Na produces 1 mole of H2 from the equation reaction.
Thus, since 8.2 L of hydrogen gas at STP are produced. And we know that at STP, 1 mole of a gas will have a volume of 22.4 L, and also, We know according to avogadro's number that, 1 mol = 6.02 × 10^(23) atoms, Thus;
8.2 L of H2 × (1 mole of H2/22.4 L) × (2 mole of Na/1 mole of H2) × (6.02 × 10^(23) atoms/1 mole of Na) = 4.4 × 10^(23) atoms
The starting substances in a chemical reaction are called reactants - they are written on the left side of a chemical equation.