chemistry specification part 1

Question 1

how can you reduce the risk and hazards in an experiment?

Answer 1

-use low concentrations of substances used
-gloves and goggles

Question 2

why do we use hazard symbols?

Answer 2

to inform people about safe-working precautions with these
substances in the laboratory.
To warn people of dangers with substances

Question 3

how has the dalton model changed over time due to new discoveries?

Answer 3

-added electrons, protons, neutrons and shells

Question 4

Explain why atoms contain equal numbers of protons and
electrons

Answer 4

because atoms are neutral and have no charge. Protons and electrons cancel each other out

Question 5

what is mass number?

Answer 5

protons + neutrons

Question 6

what makes each element unique?

Answer 6

the number of protons they have

Question 7

what is an isotope?

Answer 7

different atoms of the same element
containing the same number of protons but different numbers
of neutrons in their nuclei

Question 8

how did Mendeleev predict the existence of elements not yet discovered?

Answer 8

Mendeleev left gaps in his table to place elements not known at the time. By looking at the chemical properties and physical properties of the elements next to a gap, he could also predict the properties of these undiscovered elements.

Question 9

how did Mendeleev arrange the periodic table?

Answer 9

had arranged elements in order of increasing relative atomic mass but this was not always true because of the relative abundance of isotopes of some pairs of elements in the periodic table

Question 10

what is the atomic number?

Answer 10

number of protons