The periodic table Flashcards
What was the basis for organizing elements before the discovery of protons, neutrons, and electrons?
Approximate weights of atoms relative to each other and their physical and chemical properties
Observations made during experiments about how atoms reacted were crucial for this organization.
Who first listed the elements in order of atomic weight and noticed the law of octaves?
John Newlands
He observed that every eight elements had similar properties.
What were some limitations of John Newlands’ periodic table?
• No gaps for undiscovered elements
• The law of octaves wasn’t always followed
• Some elements were incorrectly grouped based on atomic weight instead of properties.
In what year did Dmitri Mendeleev create a more accurate periodic table?
1869
Mendeleev’s table was an improvement over Newlands’ due to his predictive approach.
What two main strategies did Mendeleev use to improve the periodic table?
• Left gaps for undiscovered elements by predicting their properties
• Swapped elements that didn’t fit their group based on properties.
How is the modern periodic table organized?
In order of atomic number (number of protons)
This organization reflects the discovery of protons, electrons, and neutrons.
What does the arrangement of elements in the same group indicate?
They have the same number of electrons in their outer shell.
What determines an element’s reactivity?
The number of electrons in their outer shell.
What do elements in the same period have in common?
They have the same number of shells/energy levels.
Why is atomic number preferred over atomic weight for organizing the periodic table?
Atomic weight didn’t work due to isotopes; atomic number only counts protons.
What feature of the periodic table separates metals from non-metals?
A staircase line.
What are some characteristics of metals?
• React to form positive ions
• Conduct electricity
• Metal oxides are always basic.
What do non-metals not form when they react?
Positive ions
Non-metals typically do not lose electrons to form positive ions.
Which form of carbon conducts electricity?
Graphite and graphene
These are exceptions among non-metals.
What type of oxides do non-metals form?
Acidic oxides
Non-metals typically produce acidic oxides when they react.
What are the noble gases?
Helium, Neon, Argon, Krypton, Xenon, Radon
These elements are known for their inertness due to having a full outer electron shell.
What is the electron configuration of noble gases?
8 electrons in the outer shell (except Helium has 2)
A stable arrangement of electrons contributes to their inertness.
What happens to the size of noble gas atoms as you move down the group?
The size increases
This is due to more electrons and additional electron shells.
What trend is observed in the boiling points of noble gases as you move down the group?
Boiling points increase with relative atomic mass
More electrons lead to greater forces of attraction between atoms.
List two uses of Helium.
- Balloons
- Cooling superconducting magnets
Helium is valued for its low density and non-reactivity.
What are the alkali metals?
Lithium, Sodium, Potassium, Rubidium, Caesium, Francium
These elements belong to Group 1 of the periodic table.
How many electrons do alkali metals have in their outer shell?
1 electron
This makes them highly reactive.
What physical characteristics do alkali metals have?
Soft with low density
These metals are generally easy to cut and are less dense than water.
What type of compounds do alkali metals form?
Colourless compounds
These compounds often result from their reactions with non-metals.
What happens to the atomic size of alkali metals as you go down the group?
The atomic radius increases
More electron shells lead to an increase in size.
What is the trend in reactivity of alkali metals as you move down the group?
Reactivity increases
The outer electron becomes easier to lose due to distance from the nucleus and increased shielding.
True or False: A cation is larger than the original atom.
False
A cation is smaller as it loses electrons and has one fewer electron shell.
What do Group 1 metals form when they react with water?
A metal hydroxide (an alkali) and hydrogen gas
This reaction is characteristic of alkali metals.
What happens when lithium reacts with water?
Floats, steadily gives off effervescence, eventually disappears
Lithium produces hydrogen gas during the reaction.
Describe the reaction of sodium with water.
Floats, moves about, melts to a sphere, effervescence, eventually disappears
Sodium reacts vigorously with water, generating heat and hydrogen.
What occurs during the reaction of potassium with water?
Floats, moves about, vigorous reaction, effervescence, lilac flame, eventually disappears
Potassium’s reaction is more vigorous compared to lithium and sodium.
What do Group 1 metals form when they react with oxygen?
Metal oxides
The reaction is a redox process involving oxidation and reduction.
What occurs at room temperature when Group 1 metals react with oxygen?
Form a white solid oxide covering the surface
This oxide can inhibit further reaction with oxygen.
What happens when alkali metals are heated in oxygen?
Burn vigorously, forming oxide as a white smoke
The reaction produces metal oxides that can be hazardous.
What are the products of Group 1 elements reacting with chlorine?
Chlorides, which are white solids at room temperature and dissolve in water to form colourless solutions
These reactions are highly exothermic.
What are two characteristics of transition elements compared to normal metals?
Higher melting points and densities; stronger and harder
Transition metals have distinct physical properties that differentiate them from alkali and alkaline earth metals.
How do transition metals differ in reactivity compared to normal metals?
Much less reactive and do not react as vigorously
This lower reactivity contributes to their use in various applications, including catalysts.
What type of ions do transition metals form?
Transition metals form ions with different charges, e.g., Fe2+ and Fe3+.
What characteristic is common to transition metals in terms of their compounds?
Transition metals usually form coloured compounds.
What is an example of a catalyst used by transition metals?
Iron in the Haber process to make ammonia.
What are the halogens?
Group 7 elements that are diatomic molecules.
How many electrons do halogens have in their outer shell?
7 electrons.
What do halogens want to do to achieve a full outer shell?
Gain an electron.
What are the colours of the halogens?
- Fluorine: pale-yellow gas
- Chlorine: green gas
- Bromine: red-brown liquid
- Iodine: grey solid or purple vapour.
What trend occurs in reactivity as you go down group 7?
They become less reactive.
What makes it harder for halogens to gain an extra electron as you go down the group?
The outer shell is further from the nucleus and there is increased shielding by inner shells.
What happens to the melting and boiling points of halogens as you go down the group?
They have higher melting and boiling points.
How do the relative atomic masses of halogens change down the group?
They have higher relative atomic masses due to more protons.
What type of reaction occurs when halogens react with metals?
A redox reaction producing salts (halides).
What type of bonds hold halides (salts) together?
Ionic bonds.
What is the result of a halogen reacting with a non-metal?
A covalent compound called a non-metal halide (e.g., hydrogen chloride).
What occurs in a displacement reaction involving halogens?
A more reactive element takes the place of another in the salt.
