Answer: The ion is 
. The chemical symbol of the noble gas this ion is isoelectronic with Kr.
Explanation:
The given electronic configuration is,
The number of electrons = 2 + 2 + 6 + 2 + 6 = 18 electrons
As the ion has a charge of +2 , that means it has lost two electrons so the the neutral element will have 2 more electrons i.e 18+2 = 20. The element has atomic number of 20 and the element will be Calcium with electronic configuration of
Thus the symbol of ion is . the nearest noble gas with 18 electrons is Krypton with symbol Kr.
Answer:
The answer to the question is
50 % of the original amount of potassium 40 will be left after one half life or 1.25 billion years
Explanation:
To solve the question we note that the half life is the time for half of the quantity of substance that undergoes radioactive decay to disintegrate, thus
we have
half life of potassium 40 K₄₀ = 1.25 billion years
To support the believe tht the rock was formed 1.25 billion years ago we have
After 1.25 billion years we have
= 
=0.5 of 
will be left or 50 % of the original amount of potassium 40 will be left
Answer:
2H2O2(aq)→ 2H2O(l) O2(g) : The oxidation number of oxygen for each compound is -1, -2, 0
Explanation:
In peroxides the oxidation state of oxygen is -1, since one oxygen bonds to the other oxygen and a hydrogen and the bound oxygen captures the electron of the remaining hydrogen. Through a scheme would be
H --- O --- O --- H
We remember that oxygen needs two electrons to get to have the configuration of the nearest noble gas (Lewis octet rule). In Peroxides, the oxygen is linked by covalent bonds. If we take it strictly, peroxide is a grouping of two oxygen, having the whole valence -2. which is why it is usually said that it is when oxygen has a valence -1
As we said the oxidation state is -2, the one that appears in the water molecule, since Hydrogen acts with valence +1 and it is 2 atoms that give up electrons to compensate for oxygen.
In the O2 it acts with valence 0 since we talk about gas in its elementary state. All diatomic molecules in their elemental state, generally gases or metals in solid state, act with a valence of 0.
Answer:
16.8dm3
Explanation:
2 moles of CO gives 1 mole of N2
2 moles of CO= 2* 28= 56g
1 mole of N2 = 1* 22.4dm
56g of CO gives 22.4dm3 of N2
42.7 of CO will give> (42.7*22.4)/56
=16.8dm3
Since we are already given the balanced equation:
→ 
We can derive the molar ratios as: 1:2:1:1
That being said, we are given 0.172 moles of bromine (
), so it has a ratio of 1:1 with sodium bromide (
).
So we can take from that ratio, that when 0.172 moles of bromine are used, we are, in turn, going to get 0.172 moles of sodium bromide produced.
