Answer:
This question lacks options, the options are;
A. Absorption of heat
B. A chemical change
C. A physical change
D. Formation of a new compound
The answer is C. A physical change
Explanation:
A physical change is a type of change that does not involve the chemical composition of the substance(s) involved. Physical changes affect the form but not the chemical content of a substance. Examples of physical changes are freezing, change of state, boiling etc.
In this question, a liquid is cooled during an investigation causing it to solidify. The cooling of this liquid represents a PHYSICAL CHANGE because the liquid state of the substance is only changed to a solid state but does not involve changing the chemical composition of the substance.
From the periodic table, beryllium has an atomic number 4. This means that beryllium has 4 electrons.
Now, the first energy level can hold only 2 electrons (which will occupy the s sublevel) wile the remaining two electrons will occupy the second energy level (also in the s sublevel).
Based on the above, the electronic configuration of beryllium will be as follows:
1s2 2s2
Answer:
The most important resonance structure is 4 (attached picture). Its bon order is
or
.
Explanation:
A picture with 4 forms of the perchlorate structure is attached. The first structure has simple bonds. The second structure contains a double bond, the third structure has two double bonds and the fourth structure has three double bonds.
Formal charge = group number of the periodic table - number of bonds (number of bonding electrons / 2) - number of non-shared electrons (lone pairs)
The formal charges in the first structure is +3 in chlorine and -1 in oxygen.
The formal charges in the second structure is +2 in chlorine, -1 in oxygen and 0 in the double bond oxygen.
The formal charges in the third structure is +1 in chlorine, -1 in the single bond oxygens and 0 in the double bond oxygens.
The formal charges in the fourth structure is 0 in chlorine, -1 in the single bond oxygen and 0 in the double bond oxygens.
The most important resonance structure is given by:
- Most atoms have 0 formal charge.
- Lowest magnitude of formal charges.
- If there is a negative formal charge, it's on the most electronegative atom.
Hence, the fourth structure is the mosr important.
The bond order of the structure is:
Total number of bonds: 7
Total number of bond groups: 4
Bond order= 