Atomic Structure+ Isotopes Flashcards
What is the mass of an electron?
Almost 0
What is the charge of an electron?
-1
What is the mass of a proton?
1
What is the charge of a proton?
+1
What is the mass of a neutron?
1
What is the charge of a neutron?
0 (neutral)
What is the mass number in an element?
Number of protons+ neutrons
What is the atomic number of an element?
Number of protons
What is an isotope?
An atom with the same number of protons but different number of neutrons
How have the ideas of atoms changed over time?
- originally spheres that could not be divided into anything smaller
- now known to have a nucleus (made up of protons and neutrons) surrounded by electrons that orbit in their energy levels.
What are the three subatomic particles that make up an atom?
Proton+ electron+ neutron
Compare the difference in size of protons, neutrons and electrons.
- protons and neutrons= same size
- electrons are much smaller
What is the size of an atom?
1 times 10 to the power of -10 in diameter
Compare the size of a nucleus to the size of an atom
Diameter of nucleus about 10 thousand times smaller than atom
Compare the size of an electron with a nucleus
Diameter at least 1 thousand times smaller than that of nucleus
What is the overall charge of atoms of an element containing equal number of protons and electrons?
no overall charge
True or false: protons, neutrons and electrons are evenly distributed in an atom?
False they are not evenly distributed in an atom
Describe the structure of an atom.
- protons and neutrons exist in a dense core at the centre of the atom (nucleus)
- electrons spread out around edge of the atom and orbit the nucleus in shells
Describe the structure of a sodium atom, include masses and charges of all particles. ( mass number=23 atomic number= 11)
- sodium has 11 POSITIVE PROTONS
- sodium has 11 NEGATIVE ELECTRONS
- sodium has 12 NEUTRONS
- PROTONS AND NEUTRONS both have a mass of 1 and are found in nucleus
- ELECTRONS have NO MASS and orbit in shells.
- arrangement in sodium is 2,8,1
What happens to electrons if electromagnetic radiation is absorbed by the atom?
Move up energy levels
What happens to the electrons if electromagnetic radiation is emitted by the atom?
Electrons move down energy levels
Describe how a money detector works in 3 steps.
- banknotes contain strip of paper to show they are genuine
- when uv light (electromagnetic radiation) is absorbed, electrons become excited+ move to higher energy levels
- when they fall back down visible light (electromagnetic radiation) is emitted and the strip glows
What is ionising radiation?
If enough energy is ABSORBED then electrons may be lost completely+ positive ions formed
True or false: isotopes have the same proton number
true- if they didn’t they wouldn’t be the same element
Who created the original thought of atoms being spheres that could not be divided into anything smaller?
John dalton
Who found that electrons could be removed from atoms?
JJ Thomson
Who created the plum pudding model?
JJ Thomson
Describe the plum pudding model
Atoms were thought to have a cloud of positive charge with electrons dispersed throughout this cloud
What experiment did enterst Rutherford and Ernest marsden carry out?
The alpha particle scattering experiment
What subatomic particles did Rutherford discover?
Protons
What did Bohr propose in the atomic structure?
That the electrons orbit the nucleus at specific distances
What did James Chadwick discover?
Neutrons (in the nucleus)
When was the first discovery of atoms?
1803
When was the plum pudding model discovered?
1897
Who and when was the nucleus model discovered?
1909 by Ernest Rutherford
When was the Bohr model discovered?
1913
When was the atomic structure we use now discovered and by who)
James Chadwick in 1932
What are two similarities of the nuclear model and the plum pudding model?
- both contain positive charge
- both have electrons
What is the 4 difference of the plum pudding model and the nuclear model?
- positive charges spread out in plum model but only in NUCLEUS of nuclear model
- electrons spread through atoms in plum model and only in shells of nuclear model
- nuclear model has nucleus
- nuclear model has protons and neutrons
Describe the alpha particle scattering experiment in two steps
- Rutherford used radioactive source to fire positive charges alpha particles at thin gold foil
- if atom was like plum pudding model all of particles would go straight through+ small amount of deflection
What were the three observations from the scattering experiment?
- most alpha particles went straight through= atom is mostly empty space
- some were bent off course= alpha particles hit positive charge (proton)
- very small number came back= all positive charge concentrated in small space centre of the atom
