Based on their number of valence electrons, which group of elements will gain two electrons by bonding with other atoms? Question 1 options:

Be, Mg, Ca, Sr, Ba

F, Cl, Br, I, At

O, S, Se, Te, Po

N, P, As, Sb, Bi

O, S, Se, Te, Po

Explanation:

Oxygen, sulphur, selenium, tellurium and polonium are all members of group sixteen. The elements in group sixteen all possess six electrons in their outermost shell. Recall that an atom is said to stable if it contains eight electrons in its outermost shell. This is also referred to as the octet rule. Hence atoms of elements obey the octet rule when they combine to form compounds with eight electrons present on the outermost shell of each atom.

Having six electrons on their outermost shell implies that they need to gain two electrons by bonding to other atoms of other elements. Two examples will suffice here.

Water is formed when an oxygen atom shares an electron with each hydrogen atoms.

Hydrogen sulphide is formed when sulphur share two electrons with two hydrogen atoms. Hence the answer.

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

he uptake of drugs from the intestine is often strongly influenced by diffusion. for example, consider a water-insoluble steroid for treating inflammation that is solubilized in aggregates of detergent molecules, called micelles. these micelles, aggregates of 80 soap molecules, have a molecular weight of 24,000, a diameter of 2.6 nm, and a charge of -27. the positively charge ions (counterions) in this system are na".