Chapter 1 Flashcards
What are the subatomic particles found in an atom?
protons, neutrons, electrons
What does the atomic number tell you?
The number of protons in the atom
What is the charge on a proton?
Positive
What is the charge on an electron?
Negative
How do you find the number of neutrons?
atomic mass - atomic number
Which two subatomic particles have a mass?
protons and neutrons
How do you find the number of electrons?
It is the same as the number of protons so by looking at the atomic number
What is an isotope?
It is an atom with the same number of protons and electrons but different numbers of neutrons
Isotopes of the same element have the same properties
What is a mixture?
A mixture consists of two or more elements or compounds not chemically combined together. The chemical properties of each substance in the mixture are unchanged.
Where do the electrons sit in an atom?
In shells (orbitals) around the nucleus.
How do you find the mass number of an element?
Add the protons and neutrons together
How many electrons can the second and third shells hold?
8
How many electrons can the first shell hold?
2
What is the average size of an atom?
1x10-10 m
What is atomic mass realtive to?
Different atoms have different masses. Atoms have such a small mass it is more convenient to know their masses compared to each other. Carbon is taken as the standard atom and has a relative atomic mass (Ar) of 12.
Atomic mass is defined as being one twelth of the atomic mass of a carbon-12 atom.
What was Daltons model of the atom?
Solid Sphere model - smallest unit of matter (no protons, neutrons or electrons present)
What was Thomsons model of the atom?
Plum pudding model.
Electrons embedded in positively charged matter.
Cathod ray tube experiemnt.
What was Rutherfords model of the atom?
Nuclear model.
Gold foil experiment - some +ve alpha particels were deflected at an angle and did not pass straight through.
Small positive nucleus surrounded by -ve electrons.
What was Bohrs model of the atom?
Planetary model.
Small positively charged nucleus, negative electrons move in fixed orbits (shells) around the nucleus.
What is the quantum mechanical model of the atom?
Small positively charged nuceleus, negative electrons localised into orbits (electron clouds) around the nucleus.
(Based on work by Heisenberg, deBroglie and Schrodinger)
Who discovered the presence of new uncharged particles (neutrons) in the nucleus?
Chadwick
How did Rutherfords gold foil experiment disprove Thomsons model of the atom?
It showed that there was a positive nucleus that deflected the positive alpha particles.
How would you calculatte the relative atomic mass of Chlorine using the mass and abundance of its isotopes?
HIGHER only
Chlorine’s Ar of 35.5 is an average of the masses of the different isotopes of chlorine.
The relative atomic mass of an element is a weighted average of the masses of the atoms of the isotopes.
Chlorine has two isotopes: 35Cl and 37Cl. In any sample of chlorine, 75 per cent of the atoms are 35Cl and the remaining 25 per cent are 37Cl.
Relative atomic mass (Ar) = (35x75) + (37x25) /100
What does Ar stand for?
Relative atomic mass
