unit 1: atomic structure

Question 1

describe how you would seperate rock salt to obtain salt crystals and pure dry sand

Answer 1

-add rock salt to water
-salt dissolves in water but sand does not
-use filter paper to seperate sand from the water
-we heat the salt water and get crystals of salt
-water boils off

Question 2

two advantages of using modern symbols rather than dalton’s symbols

Answer 2

-modern symbols only require a number following the element whereas Dalton’s requires drawing circles according to the number
-modern symbols can use the element from the periodic table whereas Dalton’s model you may run out of shapes

Question 3

isotopes

Answer 3

different types of atoms of the same element
-they have different number of neutrons but same number of protons and electrons

Question 4

what did the results from the alpha scattering model discover?

Answer 4

-it allowed scientists to discover that there was an a small area of positive charge in the centre, hence the deflections and bouncing back of particles
-most alpha particles passed straight through, showing there is a lot of empty space in an atom

Question 5

why would the radius of a metal ion be smaller than a radius of a metal atom?

Answer 5

-metal ions are always smaller than the atom because they lose electrons meaning the protons pull the electrons closer to themselves
-the proton number remains the same so there is a larger electrostatic force causing decrease in radius

Question 6

why would the radius of a non metal ion be larger than the radius of a non metal atom?

Answer 6

-non metal ions are always larger than the atom because they gain electrons meaning the number of electron shells orbitting the protons and neutrons increasing meaning the radius of the ion grows larger
-the proton number remains the same there is a smaller electrostatic forcing causing an increase in radius

Question 7

atom

Answer 7

smallest part of an element

Question 8

compound

Answer 8

-formed by elements being chemically reacted together
-contain 2 or more elements
-can only be seperated using chemical processes

Question 9

mixture

Answer 9

-two/more elements combined physically, not chemically combined together
-can only be seperated using physical processes:simple distillation, fractional distillation, crystilisation, chromotography

Question 10

what did the alpha scattering experiment lead to the discovery of?

Answer 10

nuclear model

Question 11

what did neil bohr do?

Answer 11

adapted the nuclear model by suggesting that electrons orbit the nucleus at specific distances

Question 12

what did james chadwick discover

Answer 12

the neutron

Question 13

why do atoms have no overall charge?

Answer 13

because every atom has the same number of protons as they do electrons meaning there +1 charge and -1 charge cancel each other out

Question 14

radius of an atom

Answer 14

1 x 10^-10

Question 15

radius of a nucleus

Answer 15

1 x 10^-14

Question 16

why are elements in the periodic table ordered based on atomic number?

Answer 16

to ensure they are in groups with elements that have similar properties