During what what phase of the moon can a lunar eclipse occur? a. new moon b. first quarter c. waxing gibbous d. full moon

The correct option is D.

Explanation: Lunar eclipse occurs when Sun, Earth and Moon all align in the same line and the plane of Earth's and Moon's orbit around the Sun are same. The light of the sun is blocked by the Earth and hence, the Earth casts its shadow on Moon. The moon passes through the Earth's shadow and is eclipsed and appears dark.

This eclipse occurs only on the night of full moon.

Full moon occurs when Sun, Earth and Moon align in the same line but the plane of the Moon is slightly tilted with respect to Earth around the Sun.

Hence, the correct option is D.

why do the isotopes of a particular element behave differently in nuclear reactions but the same in chemical reactions? chemical reactions involve changes to electrons in an atom; isotopes do not differ in electrons, and so they react the same way during chemical changes.

- 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