Topic 2: Atomic Structure

a substance that cannot be broken down into simpler substances by a chemical reaction

• all matter is composed of atoms • atoms cannot be created or destroyed • atoms of the same element are alike • atoms of different elements are different • atoms combine to form molecules

a substance made by chemically combining two or more elements. It has different properties than its constituent elements

• fired alpha particles at a piece of gold foil; some bounced back = atoms are mainly empty space and contain a positive nucleus

+1, in nucleus

-1, outside of nucleus (space outside)

0, in nucleus

number of protons plus number of neutrons in an atom

atoms of the same element with different mass numbers due to number of neutrons it contains (same electrons and protons however)

total mass/number of atoms

when an element loses an electron (cation)

when an element gains an electron anion

weight mean of all naturally occuring isotopes of an element relative to carbon-12

Y-Rays X-Rays UV Radiation Visible light R Radiation Microwaves Radio waves

contains radiation of all wavelengths within a given range e.g. visible light

discrete lines of different wavelengths and frequencies e.g. emmision or absorbtion spectra

• The emission spectrum of hydrogen atom consists of different series of lines in different regions of the electromagnetic spectrum. • The lines in an emission spectrum are produced by excited electrons falling from higher to lower energy levels: ΔEatom = hν = hc/λ. • As the energy levels of the hydrogen atom converge at higher energy as they are further from the nucleus, the lines in the spectrum also converge at higher energy/frequency. • 2–>1 is the UV series • anything to 2 is the visible light series (palmer)

• Frequency (ν) and wavelength (λ) are related by: c (speed of light) = ν λ. • The energy of a photon (Ephoton) is related to the frequency (ν) of the radiation by Planck’s equation: Ephoton = hν (the equation is given in section 1 of the IB data booklet) h is Planck’s constant (see section 2 of the IB data booklet)

the number of waves that pass a certain point

• long wavelength; short frequency; low energy

• short wavelength, high frequency, high energy

when white light is passed through hydrogen gas

by providing hydrogen gas with high voltage

minimum energy needed to remove one mole of electrons from one mole of gaseous atoms in their ground state