The Periodic Table (General) Flashcards
What is the periodic table?
The Periodic Table is a tabular arrangement of elements in order of increasing atomic number (number of protons)
Each element in the same period..
…differs from the preceding element by addition of an electron to the electron shell and a proton to the nucleus, and possess progressively different physical and chemical properties.
Elements in the same group…
…have the same number of valence electrons and possess related chemical and physical properties.
What is periodicity?
The occurrence of similar properties at regular intervals with increasing atomic number on the Periodic Table
State the Periodic Law
Properties of elements are a periodic function of their atomic numbers
Periodic Properties
Atomic Radius Ionic Radius Ionization Energy Electronegativity Electron Affinity Metallic Character Melting and Boiling Points
Atomic Radius
Half the distance between 2 nuclei of a homo-nuclear diatomic molecule or adjacent atoms
Atomic Radius trend
Increases down the group
Decreases across a period
What are the reasons for the trends in atomic radius?
As you go across a period, the radius gets smaller because electrons are in same energy level. Also, increase in proton number means more nuclear charge.
Outermost electrons are closer to the nucleus because more protons are pulling them in the same direction, whereas the electrons are scattered.
As we go down a group, each atom has another energy level so the atoms get bigger.
What are the factors affecting atomic radii trends?
- Energy Level - A higher energy level is further away.
- Charge on nucleus - More protons means higher charge which pulls electrons in closer.
- Shielding effect - electron repulsion
Explain the sizes of ions
Positive ions give out electrons and are smaller. Negative ions receive electrons and are bigger.
Which is larger? Atomic or ionic radii?
Atomic radii
What causes changes in elements as we move across the period?
Increase in nuclear charge. It makes ionization harder and the tendency to attract electrons easy.
What is Ionization Energy?
Ionization energy is the minimum energy (kJ/mol) required to remove an electron from a gaseous atom in its ground state.
Why is Ionization Energy referred to as endothermic?
Ionization energy is always endothermic, that is energy is added to the atom to remove the electron.