Atomic structure

Question 1

What are the three subatomic particles?

Answer 1

Protons, neutrons, and electrons

Question 2

What is the charge and mass of a proton?

Answer 2

Charge: +1, Mass: 1

Question 3

What is the charge and mass of a neutron?

Answer 3

Charge: 0, Mass: 1

Question 4

What is the charge and mass of an electron?

Answer 4

Charge: -1, Mass: Very small (~0)

Question 5

Where are protons and neutrons located?

Answer 5

In the nucleus

Question 6

Where are electrons located?

Answer 6

In energy levels (shells) surrounding the nucleus

Question 7

What is the overall charge of an atom?

Answer 7

Neutral, because protons = electrons

Question 8

What does the atomic number represent?

Answer 8

The number of protons

Question 9

What does the mass number represent?

Answer 9

The number of protons + neutrons

Question 10

How do you calculate the number of neutrons?

Answer 10

Mass number - Atomic number

Question 11

What is an isotope?

Answer 11

Atoms of the same element with different numbers of neutrons

Question 12

How are isotopes similar and different?

Answer 12

Same chemical properties, different mass numbers

Question 13

What is an ion?

Answer 13

An atom or molecule with a charge due to loss or gain of electrons

Question 14

How does an atom become a positive ion?

Answer 14

By losing one or more electrons

Question 15

How does an atom become a negative ion?

Answer 15

By gaining one or more electrons

Question 16

Describe Dalton’s atomic theory.

Answer 16

Atoms are indivisible spheres; different elements have different atoms

Question 17

What did Thomson discover?

Answer 17

The electron

Question 18

Describe the plum pudding model.

Answer 18

A positively charged sphere with embedded electrons

Question 19

What experiment did Rutherford and Marsden perform?

Answer 19

Alpha particle scattering experiment

Question 20

What did the alpha scattering experiment show?

Answer 20

Atoms have a small, dense, positively charged nucleus

Question 21

Describe Rutherford’s model.

Answer 21

Electrons orbit a dense, positive nucleus

Question 22

What did Bohr propose?

Answer 22

Electrons orbit the nucleus in fixed energy levels (shells)

Question 23

Why was Bohr’s model accepted?

Answer 23

It explained experimental results and spectra from atoms

Question 24

What is the current model of the atom?

Answer 24

A nucleus of protons and neutrons with electrons in shells

Question 25

Why do scientific models of the atom change?

Answer 25

New experimental evidence leads to updated theories

Question 26

How are electrons arranged in an atom?

Answer 26

In shells around the nucleus

Question 27

What is the maximum number of electrons in the first shell?

Answer 27

2

Question 28

What is the maximum number of electrons in the second shell?

Answer 28

8

Question 29

How is the electronic structure of an atom written?

Answer 29

e.g., 2,8,1 for sodium

Question 30

Why is electronic structure important?

Answer 30

It determines chemical reactivity

Question 31

Who developed the early periodic table?

Answer 31

John Newlands and later Dmitri Mendeleev

Question 32

What was Newlands’ Law of Octaves?

Answer 32

Elements repeated properties every 8th element

Question 33

Why was Newlands’ table criticized?

Answer 33

It forced elements into groups where they didn’t fit

Question 34

How did Mendeleev arrange his periodic table?

Answer 34

By atomic mass and left gaps for unknown elements

Question 35

How did Mendeleev predict new elements?

Answer 35

He used patterns to forecast their properties

Question 36

Why was Mendeleev’s table accepted?

Answer 36

His predictions were later confirmed

Question 37

What is the modern periodic table based on?

Answer 37

Atomic number (proton number)

Question 38

Why is the modern table more accurate than Mendeleev's?

Answer 38

It explains inconsistencies when arranged by mass

Question 39

What are groups in the periodic table?

Answer 39

Vertical columns that show similar chemical properties

Question 40

What are periods in the periodic table?

Answer 40

Horizontal rows showing increasing atomic number

Question 41

Why do elements in the same group react similarly?

Answer 41

They have the same number of electrons in the outer shell

Question 42

What happens to reactivity down Group 1?

Answer 42

Increases

Question 43

What happens to reactivity down Group 7?

Answer 43

Decreases

Question 44

Why do noble gases not react?

Answer 44

They have a full outer shell of electrons

Question 45

Why do atoms form ions?

Answer 45

To achieve a full outer shell of electrons

Question 46

What is the difference between mass number and relative atomic mass (Ar)?

Answer 46

Mass number is for one atom; Ar is an average of isotopes

Question 47

Why are Ar values not whole numbers?

Answer 47

They are weighted averages of isotopes

Question 48

What causes isotopes to have different physical properties?

Answer 48

Different mass due to different numbers of neutrons

Question 49

What experimental evidence led to the discovery of the nucleus?

Answer 49

Most alpha particles passed through, but some were deflected

Question 50

What is the charge of the nucleus?

Answer 50

Positive

Question 51

Why does the nucleus have a positive charge?

Answer 51

It contains protons

Question 52

Why are electrons not counted in the mass number?

Answer 52

Their mass is negligible compared to protons and neutrons

Question 53

Is the atomic number ever larger than the mass number?

Answer 53

No, because mass number includes protons

Question 54

Does a neutral atom always have the same number of neutrons and electrons?

Answer 54

No, only protons and electrons are equal in neutral atoms

Question 55

Can two different elements have the same atomic number?

Answer 55

No, atomic number defines the element