- Atoms that loss or gain electrons are called ions. There are two types of ions: cations and anions.
- Here, 2+ represents that Calcium (Ca) should gain 2 more electrons so that its number equals to that of protons.
- 3- represents that Nitrogen (N) should loss 3 electrons to equivalent with the number of protons.
- Here, anions are S^2-, P^3-, Se^2-, Br^-.
- While cations are Cr^3+, Ag^+, Li^+, Ba^2+.
- The number of protons of Magnesium (Mg) = 12
- The number of nuetrons of Mg = 12
- The number of electrons of Mg = 12
Hope you could get an idea from here.
Doubt clarification - use comment section.
If I understand this right, the two elements are Nickel and Copper, elements 28 and 28, respectively. A nickel is worth 5 cents, and a penny, originally comprised of copper, is worth one - the total being six cents.
Answer:
The First layer is the troposphere. The troposphere is what we live in. It creates weather for us. Second layer is the Stratosphere. You will find the ozone layer in it. The ozone layer helps protect us from ultraviolet radiation (UV) from the sun. In fact, the ozone layer absorbs most of the UV radiation the sun sends to us. Life as we know it wouldn't be possible without this layer of protection. Third layer is Mesosphere. The Mesosphere is very important for earth's protection. The mesosphere burns up most meteors and asteroids before they are able to reach the earth's surface. Fourth layer is Thermosphere. The Thermosphere absorbs the sun radiation making it very hot.
Explanation: I don't know if you include this one but the fifth layer is the Exosphere. Although the exosphere is the most distance layer of earth's atmosphere it is the layer that is the planet's first line of defense against the sun's rays. It is also the first layer to come into contact and protect the earth from meteors, asteroids, and cosmic rays.
Answer:

Explanation:
Here, we wnat to get the most electronegative atom
On the periodic table, electronegativity increases across a period and decrease down the group
The elements listed are in the same group
Boron is the first member of the group
Boron is the most electronegative atom in the group