atomic structure Flashcards
What are atoms?
Atoms are the smallest part of an element that can exist.
What do chemical symbols represent?
Chemical symbols represent an atom of an element.
How are compounds formed?
Compounds are formed from elements by chemical reactions.
What do chemical reactions involve?
Chemical reactions involve the formation of one or more new substances and often an energy change.
What do compounds contain?
Compounds contain two or more elements chemically combined in fixed proportions.
What is a mixture?
A mixture consists of two or more elements or compounds not chemically combined together.
How do the chemical properties of substances in a mixture compare to those in a compound?
The chemical properties of each substance in the mixture are unchanged, unlike in a compound.
How can mixtures be separated?
Mixtures can be separated by filtration, crystallisation, simple distillation, fractional distillation, and chromatography.
What was the first thought about the structure of atoms?
Atoms were thought to be tiny spheres that could not be divided.
How are elements arranged in the periodic table?
Elements are arranged in order of atomic (proton) number.
What is the significance of groups in the periodic table?
Elements with similar properties are found in the same columns, known as groups.
What do elements in the same periodic group have in common?
They have the same amount of electrons in their outer shell.
What model was proposed after the discovery of the electron?
The plum pudding model was proposed, where the atom is a ball of positive charge with negative electrons embedded in it.
What did the alpha particle scattering experiment conclude?
The experiment concluded that the mass of an atom was concentrated at the center (nucleus) and that the nucleus was charged.
Who ordered the periodic table by atomic weight?
John Newlands ordered his table by atomic weight.
What was the setup of the alpha particle scattering experiment?
A beam of alpha particles was aimed at very thin gold foil, and their passage through was detected.
What is the ‘law of octaves’ proposed by John Newlands?
Similar properties occur every eighth element.
What was observed during the alpha particle scattering experiment?
Some alpha particles emerged from the foil at different angles, and some even came straight back.
Why were the alpha particles deflected during the experiment?
The positively charged alpha particles were being repelled and deflected by a small concentration of positive charge in the atom (nucleus).
What limitation did Newlands’ periodic table have?
It broke down after calcium.
How did Mendeleev organize his periodic table?
Mendeleev ordered his table by atomic mass, but not always strictly.
Who suggested that electrons orbit the nucleus at specific distances?
Neil Bohr suggested that electrons orbit the nucleus at specific distances.
What did later experiments reveal about the nucleus?
Later experiments revealed that the positive charge of any nucleus could be subdivided into smaller particles, each having the same amount of positive charge (protons).
Why did Mendeleev leave gaps in his periodic table?
He left gaps for elements that he thought had not been discovered yet.
Why is the table called a periodic table?
Because similar properties occur at regular intervals.
Who provided evidence for the existence of neutrons?
James Chadwick provided evidence to show the existence of neutrons within the nucleus.
What was discovered that filled the gaps in Mendeleev’s periodic table?
Elements with properties predicted by Mendeleev were discovered.
How did knowledge of isotopes affect the periodic table?
It explained why the order based on atomic weights was not always correct.
What is the atomic number?
The atomic number is the number of protons in an atom of an element.
What discovery in the early 20th century changed the ordering of elements?
The discovery of electrons, protons, and neutrons led to ordering by atomic (proton) number.
Where are metals typically found in the periodic table?
Metals are found to the left and towards the bottom of the periodic table.
What are non-metals defined as in the periodic table?
Non-metals are elements that do not form positive ions.
What is the relative charge of a proton?
The relative charge of a proton is +1.
What is the relative charge of a neutron?
The relative charge of a neutron is 0.
Where are non-metals typically found in the periodic table?
Non-metals are found towards the right and top of the periodic table.
What is the relative charge of an electron?
The relative charge of an electron is -1.
What characteristic properties do alkali metals have?
They have a single electron in their outer shell.
What is the overall charge of an atom?
An atom has an overall charge of 0, so the number of protons equals the number of electrons.
What is the approximate radius of an atom?
The radius of an atom is about 0.1 nm.
How do alkali metals react with water?
They react vigorously with water to create an alkaline solution and hydrogen.
How does the radius of a nucleus compare to that of an atom?
The radius of a nucleus is less than 1/10,000 of that of the atom.
What do alkali metals produce when they react with oxygen?
They all react with oxygen to create an oxide.
What do alkali metals form when they react with chlorine?
They all react with chlorine to form a white precipitate.
What does the mass of the nucleus represent?
The nucleus holds almost all of the mass of the atom.
How do transition elements compare to group 1 elements in terms of hardness and strength?
Transition elements are harder and stronger.
How does reactivity change among alkali metals in Group 1?
The reactivity of the elements increases going down the group.
What is a notable exception regarding the melting points of transition elements?
Mercury has a lower melting point compared to other transition elements.
What is the relative mass of a proton?
The relative mass of a proton is 1.
How do transition elements react with oxygen and water compared to group 1 elements?
Transition elements are much less reactive and do not react as vigorously with oxygen or water.
What is the relative mass of a neutron?
The relative mass of a neutron is 1.
What is the mass number?
The mass number is the sum of the protons and neutrons in an atom.
How many electrons do noble gases have in their outer shell?
Noble gases have 8 electrons in their outer shell, except helium, which has 2.
Why are noble gases unreactive?
They have a stable arrangement of electrons with full outer shells.
What are the properties of the transition element iron?
Good conductor, rusts easily in air, strong and ductile.
How do the boiling points of noble gases change?
The boiling points increase with increasing relative atomic mass going down the group.
What are isotopes?
Isotopes are atoms of the same element with different numbers of neutrons.
What do halogens have in common regarding their outer shell electrons?
Halogens have seven electrons in their outer shell.
What are the properties of the transition element cobalt?
Malleable, brittle, hard with a high melting point.
How are atoms shown in the periodic table?
Atoms are shown in the periodic table by their relative atomic mass.
How do halogens exist in nature?
Halogens exist as molecules made of pairs of atoms (e.g., Cl2).
What are the properties of the transition element nickel?
Hard, malleable and ductile, fairly good conductor of heat and electricity.
What is relative atomic mass?
Relative atomic mass is an average value that takes account of the abundance of the isotopes of the element.
What type of compounds do halogens form when they react with metals?
They form ionic compounds where the halide ion carries a -1 charge.
What are the properties of the transition element copper?
Highly ductile and conductive, malleable and soft.
What type of compounds do halogens form when they react with nonmetals?
They form covalent compounds, where there is a shared pair of electrons.
What is a typical property of transition elements regarding their ions?
They have ions with many different charges.
How do the properties of halogens change down the group?
Relative molecular mass, melting point, and boiling point all increase down the group.
What is a characteristic of compounds formed by transition elements?
They form coloured compounds.
How does reactivity change among halogens in Group 7?
Reactivity decreases down the group.
Why does reactivity decrease down the group for halogens?
Halogens react by gaining an electron, and the number of electron shells increases down the group.
Why are transition elements useful as catalysts?
They facilitate chemical reactions without being consumed.
