<em>Answer:</em>
- Element: Element are pure substance consist of same type of atoms
- Compound: Form by combination of atoms of different elements.
<em>Distinguish features:</em>
- Compounds represented by chemical formula while elements are represented by symbols.
- Compounds have fixed ratios of atoms of different elements while in elements are distinguished by atomic no.
- Compounds can be converted into simple substance by chemical methods but the elements cant be converted into simpler substance by means of chemical methods.
<em>Example:</em>
- Water (H2O) is a compounds.
- Iron (Fe) is an element.
<em>Summary:</em>
- When two or more elements are mixed then compounds are formed.
Answer:
melting point and boiling point
First, we determine how many electrons can each subshell hold:
s can hold 2 electrons
p can hold 6 electrons
d can hold 10 electrons
f can hold 14 electrons
Second, we start distributing the 10 electrons on the orbitals of subshells based on the arrangement shown in the question :
1s will hold 2 electrons
2s will hold 2 electrons
2p will hold 6 electrons
All other orbitals will will hold zero electrons as the 10 were distributed among the first 2
Answer: 1s: 2
2s: 2
2p: 6
<span> 3s: 0
3p: 0
4s: 0
3d: 0
4p: 0
5s: 0</span>
That really depends on the age of the periodic table you’re referring to. Mendeleev’s original periodic table had only 50 elements. Today, the most modern Periodic table has 118 elements.
Answer: 3.0 moles of water 
are needed to react with a mole of 3.0 of Na
Explanation:
The balanced chemical reaction of sodium with water is as follows:
According to stoichiometry:
2 moles of sodium 
reacts with = 2 moles of water
Thus 3.0 moles of sodium reacts with = 
moles of water
3.0 moles of water are needed to react with a mole of 3.0 of Na
