An index fossil is a fossil that is useful for dating and correlating the strata in which it is found.
Or it is a fossil that helps you find the date where it has been found. I rephrased that.
A. They were ways Congress sought to guarantee blacks the full rights of citizenship.
Answer:
89.4%
Explanation:
Initially, there is 5.0 of the acetanilide in 100 mL of water, then the solution is chilled at 0ºC. The solubility represents the amount that the solvent (water) can dissolve of the solute (acetanilide). So, at 0ºC, 100 mL of water can dissolve till 0.53 g of the compound, the rest will precipitate and will be recovered.
So, the mass that is recovered is 5.0 - 0.53 = 4.47 g
The percent recovery is:
(4.47/5)x100% = 89.4%
Answer:
8 electrons
Explanation:
Magnesium is present on group 2.
It has 2 valence electrons.
Electronic configuration of magnesium:
Mg₁₂ = 1s² 2s² 2p⁶ 3s²
1st energy level contain 2 electrons.(1s²)
2nd energy level contain 8 electrons. (2s² 2p⁶)
3rd energy level contain 2 electrons. (3s²)
3rs energy level of magnesium is called valence shell. It contain two valance electrons. Magnesium can easily donate its two valance electrons and get stable electronic configuration.
It react with halogens and form salt. For example,
Mg + Cl₂ → MgCl₂
The loss of electron from an results in the formation of cation represented by the positive charge on the element whereas gaining of electron results in the formation of anion represented by the negative charge on the element.
The alkali earth metal beryllium (
) belongs to the second group of the periodic table. The ground state electronic configuration of is:
From the electronic configuration it is clear that it has 2 valence electrons in its valence shell (
).
After losing all valence electrons that is 2 electrons from 
orbital. The electronic configuration will be:
Since, lose of electron is represented by positive charge on the element symbol. So, the beryllium will have +2 charge on its symbol as 
.
Hence, beryllium will have 2+ charge on it after losing all its valence electrons in the chemical reaction.
