atomic structure and the periodic table Flashcards
What is the average radius of an atom?
The average radius of an atom is 0.1 nanometres.
What is the average radius of a nucleus?
The average radius of a nucleus is 0.0001 nanometres.
What are the relative masses and charges of sub-atomic particles?
sub-atomic particle - relative mas - relative charge
proton - 1 - +1
neutron - 1 - 0
electron - very small (1/1800) - -1
What is a compound?
A compound is two or more elements chemically bonded together in fixed proportions. They can only be separated by chemical reactions. They usually have different properties to the elements it’s made from.
What is a molecule?
A molecule is any element(s) chemically joined. (eg. O2)
In 2H20, what does the smaller and larger 2’s represent?
The larger number represents the molecule number. The smaller number represents the atom number.
What is a mixture?
A mixture is two or more elements not chemically bonded together. The properties of each substance is unchanged. They can be separated by physical separation techniques.
What is the chemical formula for ammonia?
ammonia - NH3
What is the chemical formula for carbon monoxide?
carbon monoxide - CO
What is the chemical formula for calcium chloride?
calcium chloride - CaCl2
What is the chemical formula for sodium carbonate?
sodium carbonate - Na2CO3
What is the chemical formula for sulfuric acid?
sulfuric acid - H2SO4
What is the chemical formula for methane?
methane - CH4
What is the chemical formula for nitric acid?
nitric acid - HNO3
Before the discovery of the electron, what did people believe the atom was?
Before the discovery of the electron, people believed the atom was a tiny sphere that couldn’t be divided.
What did the discovery of the electron lead to? Who came up with this idea?
After the discovery of the electron, Thompson came up with the plum pudding model. This is a ball of positive charge with electrons embedded within. There was no nucleus or neutrons.
What experiment did Rutherford carry out? What were the three observations and conclusions from this experiment?
Rutherford carried out the alpha scattering experiment, where he fired a beam of alpha particles at thin gold foil.
- most went straight through, so the atom is mostly empty space
- some were scattered by small angles, so the nucleus is overall a positive charge
- 1/8000 were sent straight back, so the positive charge is concentrated at the centre
- therefore, the atom is a positive nucleus surrounded by a cloud of negative electrons
What did Niels Bohr suggest?
Niels Bohr suggested that electrons orbit the nucleus at different energy levels. He conducted experiments that agreed with this.
What did James Chadwick discover?
Chadwick discovered the neutron 20 years after the nucleus became an accepted idea.
What are isotopes?
Isotopes are the same element with the same number of protons but a different number of neutrons.
What is the difference between the mass and atomic number?
The mass number is the sum of neutrons and protons in an atom. The atomic number is the sum of protons in an atom.
What is the relative atomic mass? How do you calculate it?
The relative atomic mass is the average mass taking into account different abundances.
sum of (isotope abundance x isotope mass) / 100
What do the periods and groups in the periodic table mean?
Periods are the rows in the periodic table. They represent the number of electron shells.
Groups are the columns in the periodic table. They represent the number of electrons in the outer shell.
What was the order for the early periodic table? Why were they mostly rejected?
Scientists attempted to classify the elements by arranging them in order of their atomic weights. The early periodic tables were incomplete and some elements were placed in inappropriate groups if the strict order of atomic weights was followed.
