A dipeptide is formed when 2 amino acids are joined together by a peptide linkage.
Each amino acid molecule contains an amino group ( -NH₂) and a carboxyl ( -COOH) group. During peptide formation, a carboxyl group of one amino acid reacts with amino group of the other , resulting in the formation of a linkage known as "peptide linkage". A water molecule is also eliminated in this reaction.
A general peptide formation reaction can be written as

In the above reaction, we can see a peptide linkage ( -CONH-) getting formed between 2 amino acid molecules.
In the given molecule the peptide linkage is shown by drawing a box around it. Please refer to the attached image.
If we want to know the amino acid molecules from which this peptide is formed, we will simply break the CO-NH bond.
We will add -OH group to CO part and -H to NH part to get 2 amino acid molecules as shown in the picture.
The two amino acids thus formed are Serine & Cysteine.
Serine is designated as "Ser" and Cysteine is designated as "Cys"
Therefore the given dipeptide is designated as "Ser-Cys"
If you look at the periodic table of elements, you can see that atomic number for phosphorus is 15. It means that it has 15 electrons and 15 protons total. Now you can write configuration for P which is: 1s22s22p63s23p3. or [Ne] 3s2<span> 3p</span><span>3 </span><span>
From here, you can see that it has 5 valence electrons (s2+p3).
In the periodic table of elements the number of protons+ number of neutrons is determined as atomic mass. Atomic mass of the P is 30.
number of neutrons = atomic mass-atomic number
number of neutrons = 30-15
number of neutrons= 15 </span>
The structure of <span>4-chlorophthalic acid is attached below:
4-chlorophthalic acid is a dibasic acid i.e. it has 2 replaceable hydrogen atom. As compared to mineral acids, it is a weak acid. However, as compared to aliphatic acid, it is a strong acid. This is because of resonance effect.
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Im going for d i think i took this last year
Three is simply the coefficient which tells you the amount of molecules. In this case, there are three carbon dioxide molecules. If you want to break it down further, it also means there is three carbon atoms and six oxygen atoms.
I hope this helps.