Use the electronegativity table as necessary.

Which family of elements is the most electronegative? Column
Vll
l
Vl
Vlll

Group VII

Explanation:

The electronegativity of an element is the tendency of the atoms of that element to attract electrons that are shared with other atoms.

Each element has a different electronegativity from other elements. In particular:

- Electronegativity increases as we move towards the right along the periodic table - this is due to the fact that as we move to the right, the number of valence electrons in the atom increases, and therefore the tendency of the atom to attract more electrons increases more, in order to fill the valence shell. In fact, the most electronegative group is group VII, which is the last but on one on the right (the last group on the right, VIII, is the group containing the noble gases, which do not react at all, so they do not attract electrons)

- Electronegavity also decreases as we move downward along the periodic table - this is because as we move downward, the number of shells and electrons around the atom increase, so all these electrons "shield" the nucleus (which is positively charged, so it is the one attracting the electrons from other atoms), and so the tendency to attract more electrons decreases.

So, the group of element most electronegative is

VII

when 25.0 ml of 0.700 mol/l naoh was mixed in a calorimeter with 25.0 ml of 0.700 mol/l hcl, both initially at 20.0 °c, the temperature increased to 22.1 °c. the heat capacity of the calorimeter is 279 j/°c.

the equation for the reaction is:

naoh + hcl → nacl + h₂o

moles of hcl = 0.0250 l hcl ×

0.700

mol hcl

1 l hcl = 0.0175 mol hcl

volume of solution = (25.0 + 25.0) ml = 50.0 ml

mass of solution = 50.0 ml soln ×

1.00

ml soln

= 50.0 g soln

δt=t2-t1

= (22.1 – 20.0) °c = 2.1 °c

the heats involved are

heat from neutralization + heat to warm solution + heat to warm calorimeter = 0

q1+q2+q3=0

nδh+mcδt+cδt=0

0.0175 mol ×

δh

+ 50.0 g × 4.184 j·g⁻¹°c⁻¹ × 2.1 °c + 279 j°c⁻¹ × 2.1 °c = 0

0.0175 mol ×

δh

+ 439.32 j + 585.9 j = 0

0.0175 mol ×

δh

= -1025.22 j

δh=1025.22j0.0175 mol= -58 600 j/mol = -58.6 kj/mol