1. Atomic Structure and the Periodic Table Flashcards
What are atoms?
All substances are made of atoms, which are extremely tiny.
What is the radius of an atom?
About 0.1 nanometres (1 × 10^-10 m).
What is a nanometre (nm)?
A nanometre is one billionth of a metre (1 × 10^-9 m).
Where is the nucleus located in an atom?
In the middle of the atom.
What does the nucleus contain?
Protons and neutrons.
What is the radius of the nucleus?
Around 1 × 10^-14 m.
What charge does the nucleus have?
Positive charge due to protons.
Where is most of the mass of an atom concentrated?
In the nucleus.
How do electrons move in an atom?
They move around the nucleus in electron shells.
What is the charge of electrons?
Negatively charged.
What determines the size of the atom?
The volume of the electrons’ orbits.
What is the relative mass of protons?
1
What is the relative charge of neutrons?
0 (neutral).
What is the relative charge of electrons?
-1.
What is true about the number of protons and electrons in an atom?
They are equal, making the atom neutral.
What is an ion?
An atom or group of atoms that has lost or gained electrons.
What does the atomic number represent?
The number of protons in an atom.
What does the mass number represent?
The total number of protons and neutrons in an atom.
How do you calculate the number of neutrons in an atom?
Subtract the atomic number from the mass number.
What is the relative mass of an electron?
Approximately 1/1840 or 1/2000.
What is an element?
A substance made up of atoms that all have the same number of protons in their nucleus.
What determines the type of atom?
The number of protons in the nucleus.
What is the atomic number?
The number of protons in an atom’s nucleus.
What element has one proton in its nucleus?
Hydrogen.
What element has two protons in its nucleus?
Helium.
What do we call a substance that only contains atoms with the same number of protons?
An element.
How many different elements are there approximately?
About 100.
What is the representation of atoms of each element?
A one or two letter symbol.
What does the symbol ‘C’ represent?
Carbon.
What does the symbol ‘O’ represent?
Oxygen.
What does the symbol ‘Mg’ represent?
Magnesium.
What does the symbol ‘Na’ represent?
Sodium.
What does the symbol ‘Fe’ represent?
Iron.
What does the symbol ‘Pb’ represent?
Lead.
Why do some element symbols seem odd?
They come from the Latin names of the elements.
Fill in the blank: An element consists of only one type of _______.
Atom.
What are isotopes?
Different forms of the same element, which have the same number of protons but a different number of neutrons.
How do isotopes differ from each other?
Isotopes differ in the number of neutrons and, consequently, in their mass numbers.
What is the relationship between atomic number and mass number for isotopes?
Isotopes have the same atomic number but different mass numbers.
Give an example of a pair of isotopes.
Carbon-12 and Carbon-13.
What are the neutron counts for Carbon-12 and Carbon-13?
Carbon-12 has 6 neutrons, while Carbon-13 has 7 neutrons.
What is relative atomic mass?
An average mass taking into account the different masses and abundances of all the isotopes that make up the element.
Why is relative atomic mass used instead of mass number?
Because many elements can exist as a number of different isotopes.
How do you calculate the relative atomic mass of an element?
relative atomic mass (A) = sum of (isotope abundance x isotope mass number) / sum of abundances of all the isotopes.
Fill in the blank: Isotopes of an element have different _______.
mass numbers.
Define a compound.
Substances formed from two or more elements in fixed proportions held together by chemical bonds.
What is usually required to separate the original elements of a compound?
A chemical reaction.
What typically occurs during a chemical reaction?
At least one new substance is made and a change in energy is usually measurable.
How do the properties of a compound compare to the properties of the original elements?
They are usually totally different.
What did John Dalton describe atoms as at the start of the 19th century?
Solid spheres
Dalton proposed that different spheres made up the different elements.
What significant discovery did J.J. Thomson make in 1897 about atoms?
Atoms contain smaller, negatively charged particles called electrons
Thomson’s experiments revealed that atoms were not solid spheres.
What is the ‘plum pudding model’?
An atomic model showing the atom as a ball of positive charge with electrons stuck in it
This model replaced the solid sphere idea of atomic structure.
Who conducted the alpha particle scattering experiments in 1909?
Ernest Rutherford and Ernest Marsden
Their experiments provided evidence against the plum pudding model.
What was the expected outcome of Rutherford’s alpha particle scattering experiments based on the plum pudding model?
Particles would pass straight through or be slightly deflected
The positive charge was thought to be spread out through the atom.
What unexpected results were observed in Rutherford’s alpha particle scattering experiments?
Some particles were deflected more than expected, and a small number were deflected backwards
This indicated that the plum pudding model was incorrect.
What model did Rutherford propose after his experiments?
The nuclear model of the atom
This model features a tiny, positively charged nucleus at the center.
In the nuclear model, what surrounds the nucleus?
A cloud of negative electrons
Most of the atom is considered empty space.
Fill in the blank: In the nuclear model, the nucleus contains most of the _______.
Mass
The nucleus is a concentrated positive charge.
True or False: Most alpha particles passed through the gold sheet in Rutherford’s experiments.
True
Most particles passed through empty space with few being deflected.
