Atomic structure and the periodic table Flashcards
what is the relative charge of a proton?
-1+
what is the relative charge of a neutron?
-o
what is the relative charge of an electron?
-1
what is the relative mass of a proton?
1
what is the relative mass of a neutron?
1
what is the mass of the electron?
-very small
What is an atom?
-the smallest part of an element that can exist.
What does a chemical symbol represent?
- an atom of an element, such as O for oxygen or Na for sodium.
How many different elements are there?
- about 100 different elements, which are shown in the periodic table.
What is a compound?
- two or more elements chemically combined in fixed proportions.
Name four ways mixtures can be separated?
-filtration
-crystallization
-distillation
-chromatography
What is the difference between a compound and a mixture?
-A compound is formed by a chemical reaction, and the substances are chemically bonded, while a mixture consists of two or more substances physically combined.
What did the discovery of the electron lead to in atomic theory?
- the plum pudding model, where an atom was thought to be a ball of positive charge with electrons embedded in it.
What did the alpha particle scattering experiment reveal?
- that the mass of an atom is concentrated at the center (nucleus), and the nucleus is positively charged.
Who proposed the idea of electrons orbiting the nucleus at specific distances?
- Niels Bohr proposed this idea, and his calculations agreed with experimental observations.
What is the atomic number?
- the number of protons in the nucleus of an atom, and it defines the element.
What are isotopes?
- atoms of the same element with the same numer of protons but different numbers of neutrons.
What is the mass number of an atom?
-the sum of the protons and neutrons in an atom.
What is the relative atomic mass?
-the average mass of an element’s atoms, taking into account the abundance of its isotopes.
How are elements arranged in the periodic table?
- by increasing atomic number, with elements having similar properties grouped together in columns (groups).
What do elements in the same group of the periodic table have in common?
-the same number of electrons in their outer shell, which gives them similar chemical properties.
What did Mendeleev contribute to the periodic table?
-arranged elements by atomic weight, left gaps for undiscovered elements, and predicted properties of elements that would fill those gaps.
What are metals and where are they found in the periodic table?
- elements that form positive ions and are found on the left and bottom of the periodic table.
What are non-metals and where are they found in the periodic table?
- Non-metals are elements that do not form positive ions and are found on the right and top of the periodic table.
Describe noble gases and their properties.
-in Group 0 of the periodic table.
-unreactive and have stable electron arrangements,
-eight electrons in their outer shell (except helium, which has two).
How do the boiling points of noble gases change in the periodic table?
-boiling points of noble gases increase as you go down Group 0 (with increasing relative atomic mass).
What are alkali metals, and what is their key characteristic?
- in Group 1 and have one electron in their outer shell, which makes them highly reactive.
How does reactivity change as you move down Group 1 of the periodic table?
-The reactivity of alkali metals increases as you go down Group 1.
What are halogens, and how do their properties change down Group 7?
-elements in Group 7
- they all have seven electrons in their outer shell
-Their reactivity decreases as you move down the group, and their relative molecular mass, melting point, and boiling point increase.
What is the displacement reaction in Group 7 halogens?
-A more reactive halogen can displace a less reactive halogen from an aqueous solution of its salt.
What are transition elements?
-metals with properties such as the ability to form ions with different charges, form colored compounds, and act as catalysts.
how do we calculate relative atomic mass ?
(isotope 1 mass x abundance) + (isotope 2 mass x abundance)) ÷ 100
what are physical separation techniques used to separate?
-only mixtures not elements in a compound
what is filtration used for?
-to separate an insoluble solid from a liquid
what does insoluble mean?
-the solid will not dissolve in the liquid
describe the filtration process
-we start by pouring our mixture into the filter paper
-the liquid passes through the tiny pores in the filter paper
-the solid material cannot pass through the filter paper so its trapped
-at the end we have our liquid separated from our solid
what is crystallisation used for?
-to separate a soluble solid from a liquid
how can we make crystallisation faster?
-by gently heating our solution to evaporate the water
explain the process of crystallisation e.g sodium chloride
-we have a solution of sodium chloride in water
-gently heat the solution to evaporate the liquid
-we are left with crystals of the solid - sodium chloride
what is crystallisation used for?
-separating a dissolved solid from a liquid
describe the process of simple distillation
-we place our solution with the liquid and dissolved solid into the flask
-we heat our solution using a bunsen burner
-as we heat the solution, the liquid starts to evaporate turning into a vapour
-the vapour now rises up the glass tube
-as the vapour passes over the thermometer, the thermometer reading increases
-the vapour passes into the condenser which is cold as there is circulating cold tap water around it
-this causes the vapour to condense, turning back into a liquid as it passes through the condenser
-we collect the liquid in the beaker
-we are left with crystals of our solid in the flask and our liquid in the beaker
what is simple distillation used for?
-to separate a dissolved solid from a liquid in order to keep the liquid
-to produce drinking water from sea water
what is a disadvantage of simple distillation
-it requires a great deal of energy so it’s not used to produce drinking water
what is fractional distillation used for?
-to separate a mixture of different liquids that have different boiling points
describe the process of fractional distillation
-we gently heat our mixture
-this causes both liquids to evaporate - the one with the a lower boiling point will evaporate easier
-when vapours hit fractionating column they condense and drip back into the flask repeating the process again
-this causes the vapour with lower boiling point to increase in the fractionating column
-when they reach thermometer , temperature will rise meaning they have reached condenser with lower boiling point chemical
-to get lower boiling point chemical on its own, we wait for thermometer to reach its boiling point temperature and collect substance in new beaker
-after a while temperature increases again meaning different vapour is passing through the condenser containing many chemicals
with higher boiling point
-once temperature becomes constant again, collect higher boiling point chemical on its own
why might fractional distillation be hard to carry out?
-if the two liquids have very similar boiling it may be hard to seperate them so we need to carry out several rounds of fractional distillation
what is a mixture?
-two or more elements that are not chemically combined
what is chromatography used for?
-to separate substances based on their different solubilities
why does paper chromatography work?
-each chemical in the mixture will be attracted to the paper to a different extent
-chemicals strongly attracted to the stationary phase will not move very far
-chemicals weakly attracted to the paper will move further up the paper
why do atoms have no overall charge?
-the number of electrons is the same as the number of protons
-the positive charges on the protons are cancelled out by the negative charges on the electrons
what are ions?
-atoms with an overall charge because they have gained or lost electrons
how do electrons exist?
-in energy levels ( shells)
what is the maximum number of electrons each energy shell can hold?
1st shell - 2 electrons
2nd- 8 electrons
3rd - 8 electrons
4th - 8 electrons
why are noble gases unreactive?
-they have a full outershell
what do group 1 metals react rapidly with?
-oxygen
-chlorine
-water
-this gets more rapid as we move down group 1
who proposed the plum pudding model?
-JJ thompson
what are group 1 metals called?
-alkali metals
describe how group 1 metals react with oxygen
-lithium reacts rapidly with oxygen in the air and forms the compound lithium oxide
-sodium reacts with oxygen in the air forming the compound sodium oxide and reacts more rapidly then lithium
-potassium forms potassium oxide and reacts even more rapidly than
describe how group 1 metals react with water
-lithium reacts rapidly with water and we can see effervescence or fizzing which tells us a gas is being produced
-when sodium reacts with water we also see a gas being produced and an alkaline solution forming, sodium reacts more rapidly with water than lithium
-when potassium reacts with water, the reaction is extremely rapid and a gas is produced and an alkaline solution is formed
why does reactivity increase going down group 1?
-the radius of the atom increases so there is a greater distance between the positive nucleus and the negative outer electron
-as this distance increases, the outer electron is less attracted to the positive nucleus
-the outer electron is repelled by electrons in the internal energy levels which decreases the attraction between the nucleus and the outer electron and shielding increases as we move down group 1
-the outer electron is easier to lose
What is the radius of an atom?
- About 0.1 nanometres (1 × 10⁻¹⁰ m).
What’s in the nucleus of an atom?
-Protons and neutrons.
Where are electrons found?
-In electron shells around the nucleus.
Why are atoms neutral?
-they have equal numbers of protons and electrons.
How do you calculate the number of neutrons?
-Mass number – atomic number.
What does the mass number tell you?
-The total number of protons and neutrons.
How are ionic compounds formed?
-Metal atoms lose electrons (become positive), non-metal atoms gain electrons (become negative).
What is a covalent bond?
-Non-metals share electrons to form molecules.
Why are compound properties different from elements?
-Because the atoms are chemically bonded.
What is crude oil an example of?
-A mixture of hydrocarbons.
What is the final result of chromatography called?
- A chromatogram.
What did John Dalton believe about atoms?
-They were solid spheres and different for each element.
What did Rutherford’s gold foil experiment show?
- Atoms are mostly empty space with a dense, positively charged nucleus.
What did Bohr suggest?
-Electrons orbit in fixed shells.
Who discovered the neutron?
-James Chadwick.
What are the rules for electron shells in atoms?
-Electrons occupy shells (energy levels) around the nucleus.
-Lowest energy levels fill first, i.e. shells closest to the nucleus.
-Atoms are more stable with full outer shells (like noble gases).
-Atoms with incomplete outer shells tend to react to fill them.
How were elements arranged in the early 1800s?
-Physical and chemical properties
-Relative atomic mass
What did Dmitri Mendeleev do differently when creating the periodic table?
-Arranged elements mainly by atomic mass
-Left gaps for undiscovered elements
-Switched some elements to fit their properties, e.g. iodine and tellurium
-Predicted properties of undiscovered elements
How did the discovery of isotopes support Mendeleev’s table?
-Isotopes have different atomic masses but same chemical properties, justifying why Mendeleev sometimes prioritized properties over mass.
What does the modern periodic table show?
-Elements arranged by increasing atomic (proton) number
-Shows repeating patterns in properties
-Elements with similar properties are in columns (groups)
-Rows (periods) represent full electron shells
What can we predict using the periodic table?
-Properties of unknown elements in the same group
-Trends in reactivity and boiling/melting points
What are the key differences between metals and non-metals?
-Metals: Form positive ions, conduct electricity, strong, malleable, shiny, high melting/boiling points
-Non-metals: Don’t form positive ions easily, poor conductors, brittle, dull, low density
How does the electronic structure of atoms affect reactivity?
-Atoms aim for full outer shells
-Metals (left of the table) lose electrons easily
-Non-metals (right of the table) gain/share electrons
-Reactivity depends on how easy it is to lose/gain electrons
what are properties of transition metals
-dense, strong, shiny
-Good conductors
-Can form ions with different charges
-Often coloured compounds and good catalysts
what are properties of group 1 metals?
-1 electron in outer shell
-Very reactive, low density, soft
-Reactivity increases down the group
How do Group 1 elements react with water, chlorine, and oxygen?
-Water: Vigorous reaction → hydrogen gas + alkali solution
-Chlorine: Forms white metal chloride salts
-Oxygen: Forms metal oxides (e.g. lithium oxide)
What are Group 7 elements and their properties?
-Halogens
-All have 7 electrons in outer shell
-Exist as diatomic molecules
-Coloured vapours
-Reactivity decreases down the group
How do halogens react?
-Form covalent bonds with other non-metals
-Form ionic bonds with metals → halide ions (F⁻, Cl⁻)
-More reactive halogens displace less reactive ones in solutions
What are Group 0 elements and their properties?
-Noble gases
-Full outer shell → inert and non-reactive
-Monatomic gases
-Non-flammable
-Boiling point increases down the group due to stronger intermolecular forces
