2. Atoms, elements and compounds Flashcards
difference between element compound mixture
a substance which cannot be further divided into simpler substances by chemical method.
a substance formed by the combination of two or more elements in fixed proportion.
two or more substances mixed together that can be separated by physical means.
difference between compound and mixture (5 points)
C- is a single substance, same composition, chemical change- new substance formed, properties different to component elements, components separated by chemical reactions.
M- contains two or more substances, composition can vary, no chemical change, properties of individual elements/ compounds, components separated by physical means.
structure of the atom
Define proton number
Define mass number
a central nucleus containing neutrons and protons surrounded by electrons in shells
proton number/ atomic number- number of protons in the nucleus of an atom
mass number/nucleon number- total number of protons and neutrons in the nucleus of an atom
relative charges and relative masses of a proton, a neutron and an electron
mass- 1, 1, 1/1837
charge- +1, 0, -1
periodic table pattern- noble gas, group and period.
Group VIII noble gases have a full outer shell
the number of outer shell electrons is equal to the group number in Groups I to VII
the number of occupied electron shells is equal to the period number
define isotopes and it’s features
different atoms of the same element that have the same number of protons but different numbers of neutrons.
isotopes of same element have the same chemical properties because they have the same number of electrons and therefore the same electronic configuration.
define relative atomic mass and relative molecular mass
relative atomic mass, Ar- the average mass of the isotopes of an element compared to 1/12th of the mass of an atom of 12C
relative molecular mass, Mr- the sum of the relative atomic masses.Relative formula mass, Mr, will be used for ionic compounds
