periodic trends

In the modern periodic table, elements are arranged according to

• decreasing atomic mass
• Mendeleev's original model
• Increasing atomic number
• when they were discovered

Group 17 elements, the halogens, are the most reactive of the nonmetal elements because they

• require only one electron to fill their outer energy level
• have the highest ionization energies
• have the largest atomic radii
• are the farthest to the right in the periodic table 

The periodic law states that

• the chemical properties of elements can be grouped according to periodicity 
• the properties of the elements are functions of atomic mass
• all elements in the same group have the same number of valence electrons
• all elements with the same number of occupied energy levels must be in the same group 

As you move left to right across Period 3 from Mg to Cl the energy needed to remove an electron from an atom

• generally increases
• generally decreases
• does not change
• varies unpredictably 

The noble gases have

• high ionization energies
• high electron affinity
• large atomic radii
• a tendency to form both cations and anions 

Which electron configuration is not correct?

• O^2-  =              [He] 2s²2p⁶
• Mg²⁺ =           [He] 2s²2p⁶  
• V³⁺ = [Ar] 3d²
• Al³⁺ = [Ar] 2s²2p⁶

Does atomic radius increase or decrease as you move down a group of the periodic table?

• increase
• decrease
• unable to determine
• unchanged 

What is electron affinity?

• Half the distance between two nuclei of a covalent bond  
• How much energy is necessary to remove an electron from an atom
• How the energy changes when an atom gains an electron
• The ability to attract electrons