1c and 1d iGCSE Chemistry

atom

smallest particle of an element that can take part in a chemical reaction

molecule

particle made of two or more atoms chemically bonded together

atomic number

number of protons in the nucleus of an atom

mass number

total number of protons + neutrons in the nucleus of an atom

isotope

atoms of the same element that have the same atomic number but different number of neutrons

state the relative mass of protons, neutrons and electrons

protons: 1

neutrons: 1

electrons: 1/2000

describe how elements are organised into groups

number of electrons on the outer shell determines the element’s group number

describe how elements are organised into periods

number of occupied electron shells determines the element’s period number

relative atomic mass

weighted average mass of an atom of an element compared to 1/12th the mass of an atom of carbon 12

why do Group 1 elements have similar properties?

• chemical reactions involve the movement of the outer electrons

• because they each have one electron in their outer shell, they will all react in similar ways

State how elements are arranged in order in the modern Periodic Table

in order of increasing atomic number / proton number

ion

changed particle formed when atoms lose or gain electrons

metals always form…

positive ions by losing electrons

non-metals always form…

negative ions by gaining electrons

Why are noble gases inert(unreactive)?

they have a full outer shell of electrons so they don’t need to gain or lose electrons in chemical reactions to become more stable

ionic compound

• compound made of oppositely charged ions

• there is a force of attraction between the oppositely charged ions —>holds ions together; called ionic bond

describe the structure of an ionic compound

has a giant lattice structure; regular arrangement of millions of oppositely charged ions attracted together