Chemistry, 18.08.2019 16:50 stef76

Why is the radius of a positive ion always less than the radius of its neutral atom? (a) the nucleus pulls the remaining electrons in closer.
(b) the number of principal energy levels is always reduced. (c) the atomic orbitals contract all by themselves (d) electron speeds are reduced

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Answer from: bheam12

Positive ions are positive because they have lost electrons.
(A)-This sounds accurate, but is actually not true. When an atom loses an electron and forms a positive ion, there will be less negative charge from the electrons to attract the positively charged nucleus. Losing electrons will actually decrease the attraction between the electrons and the nucleus.
(B)-This is true in some cases, but not all. If, for example, sodium were to lose an electron, it would drop down to having its largest orbital being in the second energy level, and would decrease in size. If magnesium were to lose an electron, it would still have one electron in the third energy level, so it wouldn't drop down an energy level.
(C) and (D)-Not sure where these answers even came from.

The actual reason behind the radius of a positive ion being smaller than the radius of its neutral atom is that the repulsive force between the electrons themselves is decreased, causing them to move closer together.

Answer from: Quest

11 players on a field that has a maximum of 11 players

Answer from: Quest

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

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Why is the radius of a positive ion always less than the radius of its neutral atom? (a) the nucleu...