Answer:
e. 18
Explanation:
A neutral P atom has an atomic number of 15, which means there are 15 protons in the atom. In order to be neutral, the P atom must also have 15 electrons.
The P³⁻ anion has 3 electrons more than the neutral P atom since it has a charge of -3.
Thus, the total number of electrons are 15 + 3 = 18 electrons.
Answer: a) 
b) 
c) 
d) 
Explanation:
General representation of an element is given as:_Z^A\textrm{X}
where,
Z represents Atomic number
A represents Mass number
X represents the symbol of an element
Mass number is defined as the sum of number of protons and neutrons that are present in an atom.
Mass number = Number of protons + Number of neutrons
In an atom, when neutrons or protons are lost or gains, it directly affects the mass number of an atom.
Atomic number is defined as the number of protons or number of electrons that are present in an atom.
It is characteristic of a particular element.
Atomic number = Number of electrons = Number of proton
a) Z 74, A 186: 
b) Z 80, A 201: 
c) Z 34, A 76: 
d) Z 94, A 239.: 
Answer:
I think the right answer is c/ number of atomic orbitals
Double replacement :
2Na₃PO₄+3CaCl₂⇒6NaCl + Ca₃(PO₄)₂
<h3>Further explanation</h3>
1. A single replacement reaction is a chemical reaction in which one element replaces the other elements of a compound to produce new elements and compounds
2. Double-Replacement reactions. Happens if there is an ion exchange between two ion compounds in the reactant to form two new ion compounds in the product
3. Combination/syntesis : 2 or more reactants combine to form a new compound
4. Decomposition : the reactant is decomposed into 2/more products
If we look at the reaction options available, all of them can be included in the double replacement reaction, but we only choose the reaction from Sodium phosphate and Calcium chloride which leads to options: C because it is balanced (from the number of atoms in the same reactant and product) and is in accordance with the chemical formula of each compound (both products and reactants)