development of the periodic table

Question 1

what does the word periodic mean?

Answer 1

occurs at regular intervals

Question 2

in the periodic table, what occurs at regular intervals?

Answer 2

elements with similar properties

Question 3

what similiar properties do elements in group one have?

Answer 3

consists of highly reactive metals

Question 4

what similiar properties do elements in group 7 have?

Answer 4

highly reactive NON-metals

Question 5

all the elements in a group have what similiarity?

Answer 5

similar chemical properties (reacts in a similiar way)

Question 6

why do all elements in the same group react in a similiar way

Answer 6

they have the same number of electrons in their outer energy level

Question 7

what main scientists had attempted to rearrange the elements on the periodic table in some sort of order?

Answer 7

Dobereiner
John newlands
Dmitri mendeleev

Question 8

what did the scientist döbereiner discover?

Answer 8

triads
he noticed that elements with similiar chemical properties often occurred in threes
he called these triads

Question 9

lithium sodium and potassium are a good example of what, according to dobereiner?
why?

Answer 9

triads

they have similar chemical properties such as how they all react rapidly with water

Question 10

dobereiner finding triads in metals and triads in non metals lead to scientists wondering what?

Answer 10

if these elements could be arranged into some sort of logical order

Question 11

around 40 years later after döbereiner, which scientist had a new discovery on the development of the periodic table?

Answer 11

John Newlands

Question 12

what did scientist john newlands do?

Answer 12

arrange the elements in order of INCREASING ATOMIC WEIGHT.

Question 13

what was the law of octaves

Answer 13

when elements are arranged in the increasing order of atomic weights, every eighth element has similar properties to the first.

Question 14

what were some problems of newlands order?

what did this mean in science?

Answer 14

by always sticking to the exact order of atomic weight, sometimes elements grouped together even though they had totally different properties.
this meant that Newlands law of octaves was not really taken seriously by other scientists

Question 15

what did dmitri mendeleev develop?

Answer 15

the first modern periodic table

Question 16

how did mendeleev arrange the elements on the periodic table?
how is his arrangement of the periodic table different to the others?

Answer 16

he started by order of increasing atomic weight
he then did 2 things no one had done before
-if needed, he would switch the order of specific elements so they fit the patterns of other elements in the same group
-realised that some elements hadn’t been discovered so he left SPACES for them
what else?
he was so sure his table was correct that he predicted the properties of the undiscovered elements based on other elements in the same group

Question 17

why do scientists accept mendeleev s table to be correct?

Answer 17

the missing elements had been discovered

their properties matched mendeleevs prediction

Question 18

what is different about mendeleevs table and the modern period table?

Answer 18

modern periodic table

- elements are arranged in order of ATOMIC NUMBER (number of protons)

Question 19

why didn’t mendeleev order his table in order of atomic number?

Answer 19

protons were not discovered at the time

atomic number = number of protons

Question 20

why is mendeleev ordering his elements by atomic weight a problem?

Answer 20

elements can appear in the wrong order due to the presence of ISOTOPES
the modern periodic table has group 0
the noble gases which weren’t discovered when mendeleev published his table

Question 21

what group did mendeleev not include in his table?

why?

Answer 21

group 0-the noble gases

they had not been discovered