lesson 21 development of the periodic table

Question 1

why is it called the periodic table

Answer 1

because the word periodic means occurring at regular intervals

and in the periodic table we can see that elements with similar properties occur at regular intervals

Question 2

all of the elements in a group have what

Answer 2

similar chemical properties

(the react in similar ways)

Question 3

all of the elements in a group have the same

Answer 3

number of electrons in their outer energy levels

Question 4

the scientist Johann Döbereiner noticed what

Answer 4

that elements in similar chemical properties often occurred in threes

called triads

Question 5

after 40 years later Johann Döbereiner discovered triad, what occurred

Answer 5

the scientist John Newlands noticed something different

Question 6

what did the scientist John Newlands did what

Answer 6

ordered the elements in increasing atomic weight

Question 7

what did John Newland also see with every eighth element

Answer 7

every 8th element reacts in a similar way

Question 8

What law did Newland discover

Answer 8

law of octaves however it wasn’t really taken seriously by other scientists

Question 9

what did Dmitri Mendeleev discover

Answer 9

the first modern periodic table

Question 10

Mendeleev started by ordering all the elements in order of what

Answer 10

in order of increasing atomic weight

Question 11

if Mendeleev needed to, he’d do what

Answer 11

switch the position of all the elements

Question 12

why did Mendeleev switch the position of all the elements if needed

Answer 12

so they fitted the patterns of other elements in the same group

Question 13

Mendeleev realised to elements had not been discovered so he

Answer 13

left gaps in his periodic table where he thought an element was missing

Question 14

Mendeleev was so confident that his table was correct, so he did what

Answer 14

he predicted the properties of the undiscovered elements based on other elements in the same groups

Question 15

several years later the undiscovered properties were discovered and they

Answer 15

matched Mendeleev’s predictions

Question 16

as Mendeleev’s predictions matched the undiscovered properties, what occurred

Answer 16

other scientists accepted that Mendeleev’s table was correct

Question 17

the modern periodic table almost the exact same as Mendeleev’s apart from which important differences

Answer 17

in the modern periodic table the elements are arranged in order of atomic weight (number of protons)

Question 18

when we order by atomic number, every element is what

Answer 18

in its correct group

Question 19

when Mendeleev had discovered his table, what had not been discovered

Answer 19

protons so he ordered the elements by atomic weight

Question 20

the problem with ordering the elements by atomic weight is that

Answer 20

elements can appear in the wrong order due to the presence of isotopes

Question 21

the modern periodic table has group 0(noble gases) however these were not

Answer 21

fully discovered when Mendeleev published his table