atomic structure and isotopes

What is all matter composed of?

Atoms.

Where is most of an atom empty space?

Between the nucleus and the electrons.

Where is most of an atom's mass concentrated?

In the nucleus.

What are the three subatomic particles?

Protons, neutrons and electrons.

What is the relative charge of a proton?

+1.

What is the relative charge of a neutron?

0.

What is the relative charge of an electron?

−1.

What is the relative mass of a proton?

1.

What is the relative mass of a neutron?

1.

What is the relative mass of an electron?

1/1836.

Why is the relative mass of an electron usually considered negligible?

Its relative mass is only 1/1836 compared with a proton or neutron.

What is the charge of the nucleus?

Positive, because it contains positively charged protons.

What particles are found in the nucleus?

Protons and neutrons.

What particles are found outside the nucleus?

Electrons.

Why is an atom electrically neutral?

It contains equal numbers of positively charged protons and negatively charged electrons.

What happens when an atom gains or loses electrons?

It forms an ion.

What is an ion?

A charged particle formed when an atom gains or loses electrons.

What is a cation?

A positively charged ion formed when an atom loses one or more electrons.

What is an anion?

A negatively charged ion formed when an atom gains one or more electrons.

How is a positive ion formed?

An atom loses one or more electrons.

How is a negative ion formed?

An atom gains one or more electrons.

What determines which element an atom is?

The number of protons in its nucleus.

What is the atomic number?

The number of protons in the nucleus of an atom.

What is the atomic number also called?

The proton number.

What is the relationship between atoms of the same element?

They all have the same number of protons.

How many protons does an atom have if its atomic number is 8?

8 protons.

How many electrons does a neutral atom have?

The same number of electrons as protons.

How do you calculate the number of neutrons?

Number of neutrons = mass number − atomic number.

What is the mass number?

The total number of protons and neutrons in the nucleus.

What is the relationship between mass number and atomic number?

Mass number = protons + neutrons.

How do you calculate the number of protons?

Atomic number.

How do you calculate the number of electrons in a neutral atom?

Atomic number.

How do you calculate the number of neutrons?

Mass number − atomic number.

What are isotopes?

Atoms of the same element with the same number of protons but different numbers of neutrons.

Why do isotopes have the same chemical behaviour?

They have the same number and arrangement of electrons, giving them the same electronic structure.

Why do isotopes have different physical properties?

They have different numbers of neutrons and therefore different masses.

Do isotopes have the same number of protons?

Yes.

Do isotopes have the same number of electrons?

Yes, if they are neutral atoms.

Do isotopes have the same number of neutrons?

No.

What differs between isotopes?

The number of neutrons.

What effect does changing the number of neutrons have?

It changes the mass of the atom.

Why do isotopes generally have similar chemical properties?

Chemical behaviour depends mainly on electron arrangement, which is the same in isotopes.

Why can isotopes have different physical properties?

Different numbers of neutrons give them different masses.

What is relative atomic mass (Ar)?

The weighted mean mass of an atom of an element compared with 1/12 of the mass of a carbon-12 atom.

What is the standard used for relative atomic mass?

1/12 of the mass of a carbon-12 atom.

Why is relative atomic mass a weighted mean?

Because it takes into account both the masses and natural abundances of the different isotopes.

What does the symbol Ar represent?

Relative atomic mass.

What is relative isotopic mass?

The mass of an atom of an isotope measured relative to 1/12 of the mass of a carbon-12 atom.

What is the difference between relative atomic mass and relative isotopic mass?

Relative isotopic mass refers to one isotope, whereas relative atomic mass is the weighted mean of all naturally occurring isotopes of an element.

Why is carbon-12 used as the standard?

Its mass is defined as exactly 12 atomic mass units, making 1/12 of its mass the reference.

What does natural abundance mean?

The percentage or proportion of each isotope of an element found naturally.

How is relative atomic mass calculated?

Multiply each isotope's relative isotopic mass by its abundance, add the results, then divide by the total abundance.

What formula is used to calculate relative atomic mass?

Ar = Σ(isotopic mass × abundance) ÷ Σabundance.

An atom has atomic number 11 and mass number 23. How many protons does it have?

11.

An atom has atomic number 11 and mass number 23. How many electrons does a neutral atom have?

11.

An atom has atomic number 11 and mass number 23. How many neutrons does it have?

12.

An atom has 17 protons and 18 neutrons. What is its mass number?

35.

An atom has 17 protons. What is its atomic number?

17.

An ion has 12 protons and 10 electrons. What is its charge?

+2.

An ion has 17 protons and 18 electrons. What is its charge?

−1.

An ion has 8 protons and 10 electrons. What is its charge?

−2.

An atom loses two electrons. What type of ion forms?

A 2+ cation.

An atom gains two electrons. What type of ion forms?

A 2− anion.