So boron has an electronic configuration of 1S2 2S2 2P1 and the element with an atomic number of 3 is Lithium which has an electronic configuration of 1S2 2S1.
So the answer is 1S2 2S1.
1.the chemical change color from colorless to purple
2. A yellow gas forms
3.a brown solid forms in the bottom of the beaker
4.the temperature of the chemicals rises 15 Celsius
Explanation:
All of the options are proofs that chemical change has occurred.
A chemical change is one with the following properties:
- A new kind of matter is usually formed as seen by the gas evolution and the formation of the insoluble precipitate i.e brown solid at the bottom of the beaker.
- They are not easily reversible.
- Usually accompanied by energy changes as seen in the rise in temperature.
- Color changes can also infer chemical changes in a reaction.
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The given chemical reaction is between calcium carbonate and hydrochloric acid to produce calcium chloride, carbon dioxide and water. This reaction can be represented as,

When the concentration of the reactants is increased, the number of collisions that take place between the reactant molecules increases. This speeds up the reaction. Therefore, when the concentration of HCl is doubled as long as there is enough calcium carbonate to react with HCl, the number of effective collisions giving products increases, this causes the rate of forward reaction to increase.