The Periodic Table 1

Question 1

elements

Answer 1

a substance that cannot be split into simpler substances by chemical means (robert boyle)

Question 2

triads

Answer 2

a triad is a group of 3 elements with similar chemical properties in which the atomic weight of the middle element is aprox equal to the average of the other 2 (dobereiner)

Question 3

octaves

Answer 3

arrangement of elements in which the first and eighth elements counting from a particular element have similar chemical properties. (newlands)

Question 4

what did Humphry Davy do?

Answer 4

discovered elements by passing electricity through compounds and laid the ground work for more elements to be discovered by passing electronic currents through samples

Question 5

limitations of octaves

Answer 5

some elements werent discovered yet (noble gases) and he should have left gaps
it only worked for the first 16 elements

Question 6

limitations of triads

Answer 6

only a few were found

Question 7

mendeleev’s periodic law/system

Answer 7

when elements are arranged in order of increasing atomic mass number
the properties of the elements repeat periodically in columns of similar chemical properties

Question 8

moseley’s or modern periodic law

Answer 8

elements arranged in order of increasing atomic number
the properties of the elements repeat periodically

Question 9

advantages of modern periodic law

Answer 9

no need to reverse the order of elements to make them fall into groups of similar properties
** elements automatically fall into the correct
groups**
no gaps

Question 10

differences between mendelev and moseley

Answer 10

mendeleev:
increasing atomic mass no
only 60 elements dicovered
gaps appeared for undiscovered elements

modern
elements placed in order of increasing atomic number
more than 100 elements discovered
no gaps

Question 11

why is the periodic table useful

Answer 11

1. gives atomic and mass no of each element
2. used to calculate the relative molecular mass of molecules
3. writing electronic configuration and counting subatomic particles

Question 12

isotopes

Answer 12

atoms of the same element that have the same atomic no due to the same amount of protons and electrons but they have a different mass number due to the different no of neutrons in the nucleus.

Question 13

do isotopes react in the same way? why or why not?

Answer 13

chemical reactions are based on electrons. since different isotopes of the same element have the same no of electrons they react in the exact same way. neutrons do not effect it.

Question 14

relative atomic mass

Answer 14

the average mass no of all the isotopes of an element as they occur naturally taking their abundances into account.
relative to 1/12th of the mass of a carbon -12 isotope.

Question 15

why is the mass no on the periodic table never whole number?

Answer 15

all elements exist as a mixture of isotopes
the ram is the mean mass of all isotopes of one atom compared to the mass of 1/12th of the mass of a carbon 12 isotope.

it takes into account the amount and type of element of each isotope.

therefore the mass no is rarely a whole no as it is an average.

Question 16

what is the RAM formula

Answer 16

(% isotope 1 x mass of isotope 1)+(%I2 x M2) divided by 100

Question 17

what does it mean when a question says respectively when asking about the RAM formula?

Answer 17

that the percentages and masses go together in the order they are asked in the question

Question 18

The principle of mass spectrometry

Answer 18

charged particles moving in a magnetic field are deflected and separated by different extents or amounts according to their masses

Question 19

uses of a mass spectrometer

Answer 19

detect the presence of isotopes and identify unknown compounds.
measure the relative abundances, relative atomic mass and relative molecular mass of isotopes.

Question 20

what are the 5 stages of the mass spectrometer in order

Answer 20

vaporisation
ionisation
acceleration
separation
detection

Question 21

description of vaporisation

Answer 21

sample to be analysed is injected. the machine is kept under vacuum which converts liquids to gases

Question 22

description of ionisation

Answer 22

electron gun fires electrons at the gaseous atoms, knocking electrons from the atoms. this forms (+) charged ions.

Question 23

description of acceleration

Answer 23

(+) ions pass between (-) charged plates that attract and accelerate the (+) ions

Question 24

description of separation

Answer 24

(+) ions are deflected in a magnetic field. lighter ions are deflected more, heavier ions less. ions are separated according to their masses

Question 25

description of detection

Answer 25

(+) ions strike a detector. signal is amplified and a mass spectrum is produced

Question 26

atomic number

Answer 26

the number of protons found in a nucleus. also shows the order of elements in the periodic table.

Question 27

atomic mass number

Answer 27

the sum of number of protons and Number of neutrons in the nucleus.

Question 28

why were there gaps in mendeleev’s periodic table

Answer 28

gaps appeared for undiscovered elements

Question 29

why did mendelev reverse the order of some elements such as Te and I

Answer 29

to make them fall into groups with similar chemical properties

Question 30

in what way did mendeleev arrange his periodic table

Answer 30

In order of increasing atomic mass no and elements were placed into groups of similar chemical properties

Question 31

what else did medeleev do?

Answer 31

predicted to properties of undiscovered elements

Question 32

how did mendeleev predict the properties of undiscovered elements

Answer 32

elements were placed into groups of similar chemical properties and by knowing the properties of the other elements elements in the same group he could predict how the unknown element will behave

Question 33

explain why x ion has a charge of +/- y after it has lost z e-

Answer 33

write of the no of protons, electrons and neutrons in the ground state and the ion and then say therefore there are x more protons/e- in the ion so there are x more pos/neg charges.

Question 34

by refering to subatomic particles, explain why x and y are considered isotopes

Answer 34

give definition
show how many protons, neutrons and e- are in each