Answer is ₂₀⁴²Ca.<span>
In AZX notation
A<span> - Represents the </span>mass number of atom.
Mass number = number of
protons + number of neutrons.
<span> It is shown at
the </span>above of the left side<span> of the
atom.</span>
<span> Here it is </span>42.
<span> </span>Z - Represents the atomic number.<span>
Atomic number = number of protons.
</span><span>It is shown at the</span> bottom line of the left side of the atom.<span>
</span>Here it is 20.<span>
X - </span>Represents the symbol of the atom.<span>
<span> </span></span>Here</span> X is Ca.<span>
</span>
Answer: The freezing point and boiling point of the solution are 
and 
respectively.
Explanation:
Depression in freezing point:
where,
= freezing point of solution = ?
= freezing point of water = 
= freezing point constant of water = 
i = vant hoff factor = 1 ( for non electrolytes)
m = molality
= mass of solute (ethylene glycol) = 21.4 g
= mass of solvent (water) = 
= molar mass of solute (ethylene glycol) = 62g/mol
Now put all the given values in the above formula, we get:
Therefore,the freezing point of the solution is
Elevation in boiling point :
where,
= boiling point of solution = ?
= boiling point of water = 
= boiling point constant of water = 
i = vant hoff factor = 1 ( for non electrolytes)
m = molality
= mass of solute (ethylene glycol) = 21.4 g
= mass of solvent (water) =
= molar mass of solute (ethylene glycol) = 62g/mol
Now put all the given values in the above formula, we get:
Thus the boiling point of the solution is
The third answer because there are two of each atom
1. The reactivity among the alkali metals increases as you go down the group due to the decrease in the effective nuclear charge from the increased shielding by the greater number of electrons. The greater the atomic number, the weaker the hold on the valence electron the nucleus has, and the more easily the element can lose the electron. Conversely, the lower the atomic number, the greater pull the nucleus has on the valence electron, and the less readily would the element be able to lose the electron (relatively speaking). Thus, in the first set comprising group I elements, sodium (Na) would be the least likely to lose its valence electron (and, for that matter, its core electrons).
2. The elements in this set are the group II alkaline earth metals, and they follow the same trend as the alkali metals. Of the elements here, beryllium (Be) would have the highest effective nuclear charge, and so it would be the least likely to lose its valence electrons. In fact, beryllium has a tendency not to lose (or gain) electrons, i.e., ionize, at all; it is unique among its congeners in that it tends to form covalent bonds.
3. While the alkali and alkaline earth metals would lose electrons to attain a noble gas configuration, the group VIIA halogens, as we have here, would need to gain a valence electron for an full octet. The trends in the group I and II elements are turned on their head for the halogens: The smaller the atomic number, the less shielding, and so the greater the pull by the nucleus to gain a valence electron. And as the atomic number increases (such as when you go down the group), the more shielding there is, the weaker the effective nuclear charge, and the lesser the tendency to gain a valence electron. Bromine (Br) has the largest atomic number among the halogens in this set, so an electron would feel the smallest pull from a bromine atom; bromine would thus be the least likely here to gain a valence electron.
4. The pattern for the elements in this set (the group VI chalcogens) generally follows that of the halogens. The greater the atomic number, the weaker the pull of the nucleus, and so the lesser the tendency to gain electrons. Tellurium (Te) has the highest atomic number among the elements in the set, and so it would be the least likely to gain electrons.
Answer:
Option D. 4.02 kJ
Explanation:
A simple calorimetry problem
Q = m . C . ΔT
ΔT = Final T° - Initial T°
C = Specific heat capacity
m = mass
Let's replace the data
Q = 125 g . 2.42 J/g∘C . (34.8°C -21.5 °C)
Q= 4023.25 J
We must convert the answer to kJ
4023.25 J . 1kJ /1000 =4.02kJ
