Achemical reaction is a process by which one or more substances transform into different substances via a chemical change. sometimes, chemical reactions exhibit evidence that can be easily observed when they occur. part a which changes are evidence of a chemical reaction?

Indication/Proof: Two transparent solutions are combined and form a murky substance, A water beaker is hot to touch when applying detergent powder, Bubble forming applied to acid on chalk.

Not proof: bubbles that form in a pot of boiling water, water condensation.

- calcium has greater affinity to bond with electron receptors than hydrogen does and hence, it has the ability to replace hydrogen in most of its compounds.

- lithium has 2 valence electrons in the product because it can make only 1 bond with hydrogen. beryllium has 4 valence electrons in the product because it can only make 2 bonds. it has fewer electrons than neon and can react with electron donors. each hydrogen has 2 valence electrons, the same as helium.

- the covalent bond formed between carbon and hydrogen is polar because carbon is more electronegative than hydrogen and it attracts the bonded electron pair closer to itself, thus giving hydrogen a partial positive charge.

- a hydrogen bond is a relatively weak bond that hydrogen atoms make with the electronegative atoms nitrogen, oxygen or fluorine.

so the best choice is a.) 2 calcium (ca) atoms

a) the particles of the chair are strongly held together.