Which statement is true about elements in a period on the periodic table?

they have different properties that repeat across the next period.

they have different properties that show no pattern.

they have similar names.

they have similar properties.

They have different properties that repeat across the next period

Explanation:

Elements are distributed in groups and periods in a periodic table.

Elements in period are arranged in order of increasing atomic numbers, thus have different valence electrons and thus have different properties.

Elements that belong to same groups will show similar chemical properties because they have same number of valence electrons.

Thus as the elements are arranged such that the elements with similar chemical properties occur after a regular interval, it is true that the elements in the period have different properties that repeat across the next period.

- 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 rain shadow is a dry region of land on the side that is protected against the prevailing winds of a mountain range. the prevailing winds are the winds that occur most of the time in a particular place of the earth

prevailing winds carry air toward the mountain range. as the air rises up over a mountain range, the air cools, water vapor condenses, and clouds form. on this side of the mountains, called the windward side, precipitation falls in the form of  rain  or snow. this dry air produces a  rain shadow.