Answer:
The nuclei of most atoms also contain neutrons . The masses of subatomic particles are very tiny. ... Since the nucleus contains protons and neutrons, most of the mass of an atom is concentrated in its nucleus. Protons and electrons have electrical charges that are equal and opposite.
Answer: Although the best-known cause of a mass extinction is the asteroid impact that killed off the non-avian dinosaurs, in fact, volcanic activity seems to have wreaked much more havoc on Earth's biota. Volcanic activity is implicated in at least four mass extinctions, while an asteroid is a suspect in just one. Examples, of mass extinctions are Permian extinction of marine species, and Cretaceous extinction of various species, including dinosaurs.
The correct answer is 96.80 grams
Explanation:
The density of a substance shows the total mass the substance contains in 1 mL or 1 cm3 as density is calculated by using the formula D= M (mass) / V (volume). This implies, Iron contains 7.87 grams per milliliter. Moreover, this value and formula can be used to calculate the mass or volume of any other sample. The process to calculate the mass of an iron sample with a volume of 12.3 mL is shown below.
D = M ÷ V
7.87 mL = x ÷ 12.3 mL - x represents the missing value. Now find the value of x by solving the equation
x = 7.87 · 12.3
x = 96.80
This means a sample of 12.3 mL contains a mass of 96.80 grams. Also, you can know this value is correct because if you divide the mass by the value the density is the same (96.80 grams ÷ 12.3 mL = 7.87 g/mL)
Answer : The correct option is, electrons are not shared equally between atoms.
Explanation :
Polar covalent bond : It is a type of chemical bond in which a pair of electrons are not shared equally between the two atoms.
In polar covalent bond, the electrons are not shared equally because one atom spends more time with the electrons than the another atom. In this, one atom has more tendency to pull an electron than the other atom.
For example : 
is an example of polar covalent bond. In water molecule, oxygen spends more time with the electron than the hydrogen and oxygen carries a partial negative charge.
