Given,
The two isotopes of B are 10B and 11B
% abundance of 10B = 19.80
% abundance of 11B = 80.20
Average atomic mass of B
= 
= 
= 
= 
= 10.802
Therefore, the average atomic mass of B is 10.802 u
Remember that the:
1. Vertical columns are groups and families
2. Horizontal columns are periods
3. Period 1 has 2 e-, 2 has 8 e-, 3 has 8 e-, and 4 has 18 e-
3.The number on top of the groups/families shows what group it is on (ex. 1A, 2A, 3B, 4B, etc) and the number on top of that indicates the number of the same thing (what group it is)
⇒ ex. 1A has 1 val e-. 2A has 2 val e-. 3A has 3 val e- ( and rest goes up until 8A). Note: I skipped the transitions metals since they don't have accurate amount of val e-.
4. Know which is the mass number, atomic number, symbol, or name.
5. Where the metals, non- metals, and metalloids are located.
6. Elements on the same groups have similar properties.
7. The first group is Akali Metals and are very unstable and very reactive
8. Second group is Akaline Earth Metals
9. The middle, groups 3-12 are Transition Metal
10. Group 13 is the Boron Family.
11. Group 14 is the Carbon Family
12. Group 15 is the Nitrogen Family
13. Group 16 is the Oxygen Family.
14. Group 17 is the Halogen, salt families
15. Group 18 is the Noble Gases, and are very stable and not reactive.
I hope this helps. :)
<u>A</u><u>)</u><u> </u><u>The moles of NaOH are equal to moles of HCl.</u>
Explanation:
NaOH + HCl ↦NaCl + H20
The more solid a substance is, the less kinetic energy there is. This is because there is not a lot of space for the atoms in the solid state to move. However, in the gaseous state, the atoms are far apart with plenty of space, this lets them create a lot more kinetic energy. Solids have a lot more intermolecular forces because the atoms are together. The IMF (intermolecular force) is what lets the atoms/molecules stick together. In the solid state, all the atoms are stuck together with little to no room in between. In the liquid state, it has a lot of IMF but is weaker then the IMF in the solid state. This is why you have so much resistance when you try to move through water. In the gaseous state, there is little to no IMF because the atoms are all so far apart. This makes it easier for everyone to move around.
To answer your question more directly: As the substance is heated to its melting point, there is an increase in kinetic energy, but decrease in intermolecular forces.
