3.1 - The Periodic Table: Classification of Elements Flashcards
Group:
Elements with the same number of valence electrons and therefore similar chemical and physical properties; a vertical column of elements.
Period:
Elements with the same outer shell; a horizontal row of elements.
Which group are the alkali metals?
Group 1
List 3 physical properties of alkali metals
- Soft solids
- Very reactive
- React with water to form a basic solution of the metal hydroxide + hydrogen gas.
Which group are the alkaline earth metals?
Group 2
List 3 physical properties of alkaline earth metals
- Most abundant metal on the planet
-not as reactive as alkali metals - higher density and melting point than alkali metals
Which group are the halogens?
Group 7
List 3 physical properties of Halogens
- Gases (F and Cl), liquids (Br) and solids (I)
- Very reactive non-metal
- Form salts with alkaline metals
Which group are the noble gases?
Group 0 (or 8)
List 3 physical properties of noble gases
- Almost non-reactive
- Sometimes called rare gases or inert gases
- Gases at room temperature
List all 5 periodic trends
- Atomic radius
- Ionic radius
- First ionization energy
- Electronegativity
- Melting point
State the trend for atomic radius
Increases down a group:
- Electrons are added to energy levels farther away from the nucleus.
- Inner electrons shield the outer electrons from the positive charge of the nucleus.
Decreases across a period:
- As the protons increase, the positive charge increases; the pull increases
State the trend for ionic radius
Increases down a group:
- Outer electrons are further from the nucleus
Decreases across a period:
- The ions contain the same number of electrons but an increasing number of protons, so the ionic radius decreases.
Define first ionization energy
The energy required to remove one outer electron from a gaseous atom.
State the trend for first ionization energy
Decreases down a group:
- Electrons in higher electronic shells are further away from the positive charge of the nucleus and therefore easier to remove.
- As the distance to the nucleus increases, electrostatic force is reduced. The shielding effect also reduces the charge.
Increases across a period:
- The increasing charge in the nucleus as you move across a period exerts greater electrostatic force on the electrons; it requires more energy to remove an electron.
Define electronegativity
A measure of a tendency of an atom to attract electrons.
State the trend for melting point
Group 1:
- Decreases down a group
Group 2:
- Decreases down a group
Group 7:
- Increases down a group
Group 0 (or 8):
- Increases down a group
State the trend for electronegativity
Decreases down a group:
- The larger radius means the electrons are farther away from the nucleus, leading to decreased electrostatic attraction, so decreased electronegativity.
- Shielding effect
Increases across a period:
- Nuclear charge is increasing, atomic radius is decreasing; attractive electrostatic force that the nucleus can exert on another electron increases.
State 4 chemical properties of alkali metals
- React by losing one electron
- Reactivity increases down the group as the electron is in higher shell levels; less energy is required to remove it.
- React with water to form a metal hydroxide solution and hydrogen gas
React with halogens to form ionic salts
State 3 chemical properties of halogens
- React by gaining one electron
Reactivity decreases down the group as the valence electrons are increasingly at higher electronic shells and further from the nucleus. Plus shielding. - In displacement reactions, the more reactive (higher in the group) elements replace the less reactive ones.
Describe the test for halide ions
Adding silver nitrate solution to a solution helps detect for halides.
AgCl = White
AgBr = Cream
AgI = Yellow
