Khan Academy Atoms, Compounds And Ions

Question 1

How many carbon atoms wide is a single strand of hair?

Answer 1

You could fit approximately are one million carbon atoms a cross the width of a human hair.

Question 2

What fundamental particle defines what element an atom is?

Answer 2

The portion.

Question 3

What is the atomic number?

Answer 3

The number of protons in an atom.

Question 4

What is the difference between weight and mass in physics?

Answer 4

Mass refers to the amount of an object measured in terms of grams and kilograms etc.

Weight is the amount of force that is being exerted on your body by the earth’s gravitational field. It is measured in newtons.

So the important difference is that if you go to the moon then your mass does not change but your weight does.

Question 5

What is an Atom’s atomic mass?

Answer 5

It is a measure of mass taken in amu (atomic mass units). It is defined as one Carbon 12 has exactly the mass of 12 AMU.

Question 6

What is atomic weight?

Answer 6

Confusingly an Atoms atomic weight is a mass unit that still is measured in AMU (atomic mass unit). It is the average of what that atom would weigh accross the average of that atom on earth.

So carbon 12 is 12 AMU
But carbon 14 also exists
Since electrons also contribute to the weight you cannot conclude that carbon 14 is 14 amu.
Instead the average weight of carbon on earth is 12.011

Question 7

What is a Mole in chemistry?

Answer 7

Definition a: A Mole is 6.02x10 to the power of 23.
It is also known as Avogadro’s number.

Definition b) there is 1 Mole of (12)C atoms in 12g of carbon.

A (12)C weighs 12 amu due to the definition of an amu. If you have 6.02 x 10 to the power of 23 this will result in 12g carbon. So this number is saved as a useful constant called a Mole.

Therefore 1 gram = 1 Mole of amu.
And 1 gram = 6.02 x 10 to the power of 23 amu.
1gram of hydrogen i= 1 Mole of hydrogen because hydrogen atomic mass is 1

Question 8

What is the weight if 1 Mole of Aluminum with the mass number of 27 (rounded slightly) ?

Answer 8

A Mole of Aluminum with the mass number of 27 will be 27 grams.

A Mole is a direct translation between its mass number and a gram measurement.

Question 9

What are the different isotope names of hydrogen?

Answer 9

Protium has 0 neutrons and 1 electron
Deuterium has 1 neutron and 1 electron.
Tritium has 2 neutrons and 1 electron.

Question 10

How do you not ate an isotope?

Answer 10

With a hyphen

E. G. Carbon-13

Question 11

At what point does an atom become an ion?

Answer 11

When there are an unequal, number of protons and electrons so the atoms have a positive or a negative charge.

Question 12

What is the difference between a cation and anion?

Answer 12

Cation is positively charged and anion is negatively charged.

Question 13

How do you generally rename an ion if it becomes an anion?

E. G. Chlorine (-1)

Answer 13

You add an ide

Chloride

Question 14

What would be the name of the ionic compound that is made of potassium+1 and a chlorine - 1?

Answer 14

Potassium Chloride

Question 15

What is the difference between the empirical and molecular formula of a molecule.

Give an example with Benzene

Answer 15

Benzene
Empirical formula C1H1
Molecular formula C6H6

The molecular formula describes what is actually in each molecule. Empirical formula described the ratio.

Question 16

What is the structural formula of a molecule? Give an example with Benzene.

Answer 16

It describes the structure in which the atoms are organized

Six carbons in a hexagon. Every other bond is a double bond. Each carbon branches out to a hydrogen.

Question 17

What is molecular weight?

Answer 17

Molecular mass is the mass of a molecule as calculated by the atomic mass units of the atoms added together.

So for example the molecular mass of water is

H= 1.0079
O= 15.999
H2O = 18.015