Question

which of the following has the lowest number of unshared electrons around the central atom?
xef4
so2
clf3
h2o
sf6
question 3 (1 point)
which of the following pairs is considered to be isoelectronic?
br - and kr
h and li
k and ar
xe and i
you can use this periodic table during the quiz. however, as stated in the course outline, and in the orientation session, this quiz is not open book. you cannot access

Explanation:

Step1: Determine unshared electrons for first - part

• For \(XeF_4\): Xe has 8 valence electrons. It forms 4 bonds with F. So unshared electrons = \(8 - 4= 2\) lone - pairs = 4 unshared electrons.
• For \(SO_2\): S has 6 valence electrons. It forms 2 double - bonds with O. So unshared electrons = \(6 - 4 = 1\) lone - pair = 2 unshared electrons.
• For \(ClF_3\): Cl has 7 valence electrons. It forms 3 bonds with F. So unshared electrons = \(7 - 3= 2\) lone - pairs = 4 unshared electrons.
• For \(H_2O\): O has 6 valence electrons. It forms 2 bonds with H. So unshared electrons = \(6 - 2= 2\) lone - pairs = 4 unshared electrons.
• For \(SF_6\): S has 6 valence electrons. It forms 6 bonds with F. So unshared electrons = \(6 - 6 = 0\) unshared electrons.

Step2: Determine isoelectronic pairs for second - part

• For \(Br^-\) and \(Kr\): \(Br\) has 35 electrons, \(Br^-\) has 36 electrons, and \(Kr\) has 36 electrons. They are isoelectronic.
• For \(H\) and \(Li\): \(H\) has 1 electron, \(Li\) has 3 electrons. They are not isoelectronic.
• For \(K\) and \(Ar\): \(K\) has 19 electrons, \(Ar\) has 18 electrons. They are not isoelectronic.
• For \(Xe\) and \(I\): \(Xe\) has 54 electrons, \(I\) has 53 electrons. They are not isoelectronic.

Answer:

First question: \(SF_6\)
Second question: \(Br^-\) and \(Kr\)