Classify the following structures as Digestive, Respiratory and Excretory systems: Skin, small intestine, trachea, stomach, bladder, bronchus. (b) Define a simple machine.

Here are the answers to your questions:

10. (b) (i) How many valence electrons are in the atom?

• Assumption: Without information about the specific atom, this question cannot be answered. If referring to a common atom like Carbon, it has 4 valence electrons. If referring to Oxygen, it has 6 valence electrons. Please provide the atom's identity for a specific answer.

10. (b) (ii) What is the valency of the atom?

• Assumption: Similar to the above, the valency depends on the specific atom. For example, Carbon has a valency of 4, and Oxygen has a valency of 2. Please provide the atom's identity for a specific answer.

11. (a) Classify the following structures as Digestive, Respiratory and Excretory systems:
Skin, small intestine, trachea, stomach, bladder, bronchus.

Digestive system	Respiratory system	Excretory system
Small intestine	Trachea	Skin
Stomach	Bronchus	Bladder

11. (b) Define a simple machine.
A simple machine is a mechanical device that changes the direction or magnitude of a force. It uses a single applied force to do work against a single load force. Examples include levers, pulleys, and inclined planes.