Unit 1: Module 1-Atoms And Reactions Flashcards
Electrons: charge and position in atoms
1) They have a -1 charge.
2) They whizz around the nucleus in orbitals. The orbitals take up most of the volume of the atom.
What are atoms made up of?
Protons, neutrons and electrons
Where is most of the atom’s mass concentrated?
In the nucleus.
Nucleus: size, what you will find in it.
1) The diameter of the nucleus is very small compared to the whole atom.
2) The nucleus is where you’ll find protons and neutrons.
Why is a relative mass and relative charge used for subatomic particles?
The mass and charge of these subatomic particles is really small.
The relative mass and relative charge of each subatomic particle.
Proton: -relative mass 1 -relative charge +1 Neutron: -relative mass 1 -relative charge 0 Electron, e-: -relative mass 1/2000 -relative charge -1
What does the mass number of an element tell you?
This tells you the total number of protons and neutrons in the nucleus.
What does the atomic number of an element tell you?
1) This is the number of protons in the nucleus.
2) All atoms of the same element have the same number of protons, so it identifies the element.
Why do neutral atoms have no overall charge?
The number of electrons is the same as the number of protons.
How can you work out the number of neutrons in an element using the periodic table?
The number of neutrons=mass number-atomic number
What is an ion?
Ions have a different number of electrons than protons.
Negative ions (e.g. Br-) have ……electrons than protons.
More electrons than protons
Positive ions (e.g. Mg^2+)have…….electrons than protons.
Fewer electrons than protons
What is an isotope?
Isotopes are atoms of the same element with different numbers of neutrons.
What decides the chemical properties of an element?
The number and arrangement of electrons.
What decides the physical properties (such as densities and rates of diffusion) of an element?
The mass of the atom (isotopes can have different physical properties)
Why do we assume models of atoms are true?
When do we assume they aren’t true?
1) It fits observations and evidence we have at the time.
2) Until someone shows that a model is incomplete or wrong with evidence.
What was a problem with the atom model with its electrons arrangement and nucleus?
Electrons in a ‘cloud’ around a nucleus would spiral down into the nucleus, causing the atom to collapse.
Niels Bohr’s 4 principles of atoms:
1) Electrons can only exist in fixed orbits, or shells, not between.
2) Each shell has a fixed energy.
3) When an electron moves between shells, electromagnetic radiation is emitted or absorbed.
4) Because the energy of shells is fixed, the radiation will have a fixed frequency.
Evaluate the Bohr Model of atoms.
- -The frequencies of radiation emitted and absorbed by atoms were already known from experiments, so the model fitted these observations.
- -The model explained why some elements (the noble gases) are inert. He said that the shells of an atom can only hold fixed numbers of electrons, an elements reactivity is due to its electrons. When an atom has full shells of electrons, it is stable and does not react.
