Which of these is one way that mechanical waves differ from electromagnetic waves?
question 4 options:
mechanical waves require energy and electromagnetic waves do not.
mechanical waves require a medium and electromagnetic waves do not.
electromagnetic waves require a medium and mechanical waves do not.
mechanical waves transmit matter and electromagnetic waves transmit energy.

Electromagnetic waves differ from mechanical waves in that they do not require a medium to propagate. This means that electromagnetic waves can travel not only through air and solid materials, but also through the vacuum of space.

Mechanical waves require a medium and electromagnetic waves do not.

Hope this helps :)

Mechanical waves require a medium and electromagnetic waves do not.  

Explanation:

Electromagnetic waves are essentially a combination of electric and magnetic fields produced by the motion of charged particles. They do not require a medium to travel and can simply propagate through space. For example, light waves are electromagnetic waves

Mechanical waves are energy waves that are produced by inducing a certain disturbance in a medium. These waves require a medium to propagate and cannot travel in empty space. For example, sound waves are mechanical waves.

it is no longer used clinically

- 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