Periodic table and how the atom was formed

Question 1

Who made the plum pudding model

Answer 1

J J Thomson

Question 2

When did Thomson discover his plum pudding model

Answer 2

1897

Question 3

Explain Thomson’s plum pudding model

Answer 3

In 1897, an English physicist called J. J. Thomson discovered electrons.
Thomson modelled the atom as a ‘plum pudding’ - a ball of positive charge (dough), with negatively charged electrons (currants in pudding) mixed in with the ‘dough’.

Question 4

Who created the nuclear model

Answer 4

Ernest Rutherford

Question 5

Explain the nuclear model

Answer 5

In 1909, Ernest Rutherford discovered that alpha particles could bounce back off atoms.
Rutherford concluded that an atom’s mass is concentrated in the atom’s centre. This was called the “nucleus” and it contained positively charged particles called protons.

Question 6

Who discovered the modern model

Answer 6

neil bohr

Question 7

explain the modern model

Answer 7

Niels Bohr discovered that electrons orbit the nucleus at fixed distances.

Question 8

what is an elements atomic number

Answer 8

the number of protons it has

Question 9

where are protons found

Answer 9

in the nucleus

Question 10

where are electrons found

Answer 10

in the fixed orbit around the nucleus

Question 11

why do atoms have no overall charge

Answer 11

the total number of negative electrons equals the number of positive protons, meaning the charges cancel each other out

Question 12

what is the relative mass of protons and neutrons

Answer 12

1

Question 13

what is the relative mass of electrons

Answer 13

0.0005 which is rounded down to 0

Question 14

how do you find the relative mass in atoms

Answer 14

number of protons+ the number of neutrons

Question 15

how big are atoms

Answer 15

0.1 nanometres or 1x10 to the power of -10

Question 16

compared to an atom, how big is the nucleus in an atom

Answer 16

10,000 times smaller

Question 17

where is the mass number of an element found

Answer 17

at the top of the number

Question 18

where is the atomic number found

Answer 18

at the bottom of the number

Question 19

what is an isotope

Answer 19

an atom of the same element containing different number of neutrons

Question 20

what is the relative atomic mass

Answer 20

the average mass of all of the isotopes of an element.

Question 21

Who was the first scientist to devise a periodic table

Answer 21

John Newlands

Question 22

How was Newlands table organised/ordered

Answer 22

by the mass (atomic weight) of elements

Question 23

what was wrong with newlands table?

Answer 23

the table was incomplete and some elements were placed in inapropriate groups, elements in some groups did not react similarly with each other

Question 24

Explain Dimitri Mendeleevs periodic table

Answer 24

• Dmitri Mendeleev recognised that there may be undiscovered elements.
  Mendeleev added gaps to Newlands’ table to account for undiscovered elements.
• He also predicted the properties of these undiscovered elements and several years later, when these elements were discovered, their properties matched Mendeleev’s predictions
• He also changed the order of elements based on their atomic weight
• if he needed to, he would switch the order of specific elements, so that they fitted the patterns of other elements in that group

Question 25

briefly describe the role John Newlands played in the history of the periodic table

Answer 25

• he ordered elements in increasing atomic weight
• he saw that every eighth element reacted in a similar way (this was called the law of octaves)

Question 26

What discovery proved Mendeleev’s periodic table to be correct and Newlands’ to be wrong

Answer 26

the discovery of protons and isotopes

Question 27

where are metals found on the periodic table and why

Answer 27

they are found on the left side of the table because they have few electrons in their outer shell

Question 28

what did James Chadwick discover

Answer 28

In 1932, James Chadwick discovered that some particles in the nucleus have no charge at all. He called them neutrons.

Question 29

summarise the alpha particle scattering experiment

Answer 29

• ernest rutherford fired positively charged alpha particles at thin sheet of gold
• most particles went straight through, some deflected, and some deflected backwards

Question 30

what conclusions were made from rutherfords experiments

Answer 30

• most of the atom is empty space
• in the atom, there is a tiny, positively charged nucleus where most of the mass is concentrated, when alpha particles came in contact with it, they deflected
• if fired directly at the nucleus, they deflect backwards, otherwise they just pass straight through

Question 31

why was gold used for the alpha scattering experiment

Answer 31

because we can hammer gold into a very thin sheet, only a few atoms thick

Question 32

what charge are alpha particles

Answer 32

positive

Question 33

what are ions

Answer 33

atoms with an overall charge

Question 34

what do all elements in a group have

Answer 34

• similar chemical properties
• they react in a similar way as they have the same number of electrons on their outer shell

Question 35

differences between Mendeleev’s periodic table and the new one

Answer 35

1. in the modern periodic table, elements are arranged in order of atomic number (number of protons), and when Mendeleev discovered his table, protons had not been discovered yet, so he ordered them by atomic weight
2. The modern periodic table contains group 0, which had not fully been discovered when Mendeleev published his

Question 36

what is atomic weight

Answer 36

relative atomic mass

Question 37

one problem with Mendeleev’s table

Answer 37

he arranged elements in order of atomic weight, meaning that elements can appear in the wrong order due to the presence of their isotopes