During a lab activity a group of students was instructed to determine the density of a rock. Steps Use the balance to determine the mass of the rock. Use water displacement to determine the volume of the rock. Put 50 milliliters of water in the graduated cylinder, drop the rock in and measure the increase in the volume of the water. This will be the volume of the rock. Use the formula D=MV to calculate the density of the rock. Results Mass of the rock = 6.4 grams Volume of the rock = 0.5 mL Density = 6.40.5 = 12.8 g/mL Were the students measuring a physical property or a chemical property of the rock?

- 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

the answer is 75.0%.