FINAL Topic 2.1 - The Nuclear Atom Flashcards
define “element”
a substance that cannot be broken down into simpler substances
define “atom”
the smallest unit of an element
define “compound”
a substance made of two or more different elements that are chemically combined and have different properties from its constituent elements
example of a compound
compound for water =
2 hydrogen atoms + 1 oxygen atom =
1 compound molecule of water
Describe Rutherford’s discovery
- he shot alpha particles through a sheet of gold foil
- the alpha particles have a positive charge
- most of the particles went straight through, however, some of them repelled and bounced off an angle
- this reveals that most of the atom is empty space, however, when it collided with the nucleus (positively charged), it repelled
atoms are made up of sub-atomic particles including
protons, neutrons = nucleons
electrons = outside nucleus
- protons and electrons have an equal charge +1, -1
why are atoms neutral
the electrostatic attraction between oppositely charged sub-atomic particles prevents the electron from leaving the atom.
*number of protons (positive) = number of electrons (negative)
why are neutrons important
otherwise the positively charged protons would repel each other and the nucleus would collapse
where is the mass of an atom
majority in the nucleus as protons and neutrons are roughly 18000 times heavier than electrons
what is the atomic number
number of protons/electrons
what is the number of neutrons
atomic mass - atomic number
= mass of nucleus - number of protons
What are isotopes
atoms of the same element with a different number of neutrons and therefore a different mass
what are the difference between atoms and isotopes
the chemical properties stay the same because these are determined by the valence electrons
the physical properties differ because of the difference in mass
why is the atomic number important
it never changes and is a fixed characteristic of an element, which identifies the element
what are ions
when an atom loses or gains electrons to become electrically charged particles
why do atoms form ions
to become stable with a full valence shell
What happens when an atom loses electrons
positive ion = cation (more protons with a positive charge)
What happens when an atoms gains electrons
negative ion = anion (more electrons with a negative charge)
what is relative atomic mass of an element
the average mass of an atom of the element, taking into account all its isotopes and their relative abundance
what do you use to measure the mass of individual atoms
mass spectrometer
what does a mass spectrometer do
separates individual isotopes from a sample of atoms and determines the mass of each isotope
what is relative isotope abundance
% of an isotope of an element as it occurs
how to determine the relative atomic mass
(mass x abundance) + (mass x abundance) / 100
how is the analysis by the mass spectrometer presented in
mass spectrum
