Na 1s²2s²2p⁶3s¹
↓ - e⁻
Na⁺ 1s²2s²2p⁶ 2+2+6=10 e⁻
10 electrons are in sodium ion Na⁺
Answer:
The fourth one.
Explanation:
The fourth graph shows an object speeding up ( accelerating ) coz the velocity (tangent at the curve ) at every point is different, hence denoting an acceleration.
Answer : The correct option is, (D) double replacement reaction
Explanation :
Synthesis reaction : A chemical reaction where multiple substances or reactants combine to form a single product.
It is represented as,

Decomposition reaction : A chemical reaction in which larger reactant decomposes to give two or more than two products.
It is represented as,

Single replacement reaction : A chemical reaction in which the more reactive element replace the less reactive element.
It is represented as,

In this reaction, A is more reactive element and B is less reactive element.
Double replacement reaction : It is a type of chemical reaction where a positive cation and a negative anion of two reactants exchange places to form two new products.
It is represented as,

(X and A are the cations, Y and B are the anions)
The given reaction is:

This reaction is a double displacement reaction.