The Lewis structure for H₂CO is shown in the attached picture. The central atom is the carbon. However, I'm not sure which bond you're referring to. There can be two answers. The two C-H bonds are sp³ hybridized because it is a single bond. The C=O bond is sp² hybridized because it is a double bond.
a. Smallest basic units of matter

<u>Atom</u>: An atom is the smallest particles of a substance which may or may not exist in free state but takes part in chemical reactions.
<u>Molecule</u>: A molecule is a substance which exists in free state but doesn't take part in chemical reactions.
<u>Laws</u><u> </u><u>of</u><u> </u><u>chemical</u><u> </u><u>combination</u><u>:</u><u>-</u>
- Law of conservation of mass
- Law of constant proportions
- Law of multiple proportions
- Law of reciprocal proportions
Well weathering adds different elements to rocks which they might not be used to. For example, very hard rain & harsh winds could push a rock, causing it to fall & break off into smaller rocks.
The rock cycle is referred to as cycle because it repeats over and over again. The definition of cycle is a series of events that are regularly related in the same order. So with the rock cycle they stay in the same order and repeat.
Hope this helps :)
Answer:
Because of oxygen toxicity.
Explanation:
Oxygen toxicity.
Oxygen has been known to cause central nervous system (CNS) toxicity when the pressure gets higher. This toxicity can cause convulsions, and this can cause the diver to drown.
The current standard maximum safe oxygen working pressure is 1.4 atm ppO2. This is equal to 56.5m/185′ when breathing air (21% O2 / 79% N). Below that depth the fraction of oxygen in a breathing gas must be reduced, and in order to maintain this maximum pressure of 1.4 ppO2, Helium must be added.