N: 106Answer:
72 protons, 106 neutrons, 72 electrons.
Explanation:
to solve this use this simple method: APEMAN.
A= atomic number, P= Protons, E= Electrons.
M= Mass, A= atomic number, N= neutrons.
1. APE (atomic number, protons, electrons) are the same. since Hf (Hafnium) atomic number is 72, Hf has 72 protonsand ele ctrons.
2. to get Neutrons it will be mass-atomic number= neutrons.(M-A=N)
Hf mass= 178. So, 178-72= 106 neutrons.
Each of the terms of the sequence is a multiple of 4, starting with 4 x 1 = 4, so the rule for this sequence is 4n.
Answer:
(a)

(b)

(c)

Explanation:
(a)
The given compound is silicon tetrabromide. It means that 1 silicon and four bromine atoms are combined to form the molecule.
The chemical formula of silicon tetrabromide is 
(b)
The given compound is disulfur dichloride. It means that 2 sulfur atoms and 2 chlorine atoms are combined to form the molecule.
The chemical formula of disulfur dichloride is 
(c)
The given compound is diphosphorus hexaoxide. It means that 2 phosphorus atoms and 6 oxygen atoms are combined to form the molecule.
The chemical formula of diphosphorus hexaoxide is 
A chemist dilutes a 1.0 ml sample of 2.0M KNO₃ by adding water to it. If the concentration of the solution that is obtained is 0.0080 m, then its volume is 250mL.
<h3>How do we calculate volume?</h3>
Volume for the given equation will be calculated by using the below equation as:
M₁V₁ = M₂V₂, where
M₁ = molarity of KNO₃ = 2M
V₁ = volume of KNO₃ = 1mL
M₂ = molarity of final solution = 0.0080M
V₂ = volume of final solution = ?
On putting these values on the above equation, we get
V₂ = (2)(1) / (0.0080) = 250mL
Hence option (2) is correct.
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