2.3 elements and compounds
52. how could you distinguish an element from a compound?
*53. classify the following materials as an element, compound, or mixture. give reasons for your answers.
a. table salt (nacl)
b. salt water
c. sodium (na)
54. describe the relationship between the three items in each of the following groups. identify each item as an element, compound, or mixture.
a. hydrogen, oxygen, and water
b. nitrogen, oxygen, and air
c. sodium, chlorine, and table salt
d. carbon, water, and table sugar
55. name the elements found in each of the following compounds.
a. ammonia (nh₃)
b. potassium oxide (k₂o)
c. sucrose (c₁₂h₂₂o₁₁)
d. calcium sulfide (cas)
56. not all element names come from english or latin words. the symbol for tungsten is w from the german word wolfram. the symbol for mercury is hg from the greek word hydragyrum. use the symbols w and hg to explain the system of symbols for elements.
*57. what does the formula h₂o tell you about the composition of water?

Question

2.3 elements and compounds
52. how could you distinguish an element from a compound?
*53. classify the following materials as an element, compound, or mixture. give reasons for your answers.
 a. table salt (nacl)
 b. salt water
 c. sodium (na)
54. describe the relationship between the three items in each of the following groups. identify each item as an element, compound, or mixture.
 a. hydrogen, oxygen, and water
 b. nitrogen, oxygen, and air
 c. sodium, chlorine, and table salt
 d. carbon, water, and table sugar
55. name the elements found in each of the following compounds.
 a. ammonia (nh₃)
 b. potassium oxide (k₂o)
 c. sucrose (c₁₂h₂₂o₁₁)
 d. calcium sulfide (cas)
56. not all element names come from english or latin words. the symbol for tungsten is w from the german word wolfram. the symbol for mercury is hg from the greek word hydragyrum. use the symbols w and hg to explain the system of symbols for elements.
*57. what does the formula h₂o tell you about the composition of water?

Accepted Answer

### Question 52:
# Brief Explanations:
An element is a pure substance made of only one type of atom, e.g., hydrogen (H) has only H atoms. A compound is a pure substance made of two or more different elements chemically bonded, e.g., water ($\ce{H_2O}$) has H and O atoms bonded. To distinguish them, check the composition: elements have one atom type; compounds have multiple, bonded.
# Answer:
To distinguish an element from a compound: An element is a pure substance composed of only one type of atom (e.g., sodium, $\ce{Na}$ has only sodium atoms). A compound is a pure substance composed of two or more different elements chemically combined in a fixed ratio (e.g., table salt, $\ce{NaCl}$ has sodium and chlorine atoms bonded). So, check the composition: elements have one atom type; compounds have multiple, chemically bonded elements.

### Question 53:
#### Part a: Table salt ($\ce{NaCl}$)
# Brief Explanations:
$\ce{NaCl}$ has Na and Cl atoms bonded in a fixed 1:1 ratio, so it's a compound (pure substance, two elements, fixed ratio).
# Answer:
a. Table salt ($\ce{NaCl}$) is a **compound**. Reason: It is a pure substance made of two different elements (sodium, $\ce{Na}$, and chlorine, $\ce{Cl}$) chemically combined in a fixed ratio (1:1) through ionic bonding.

#### Part b: Salt water
# Brief Explanations:
Salt water has salt (solute) and water (solvent) mixed, not bonded, so it's a mixture (two substances, physically mixed, variable ratio).
# Answer:
b. Salt water is a **mixture**. Reason: It contains two substances (sodium chloride and water) physically mixed together (not chemically bonded), and the ratio of salt to water can vary.

#### Part c: Sodium ($\ce{Na}$)
# Brief Explanations:
$\ce{Na}$ has only sodium atoms, so it's an element (pure substance, one atom type).
# Answer:
c. Sodium ($\ce{Na}$) is an **element**. Reason: It is a pure substance composed of only one type of atom (sodium atoms).

### Question 54:
#### Part a: Hydrogen, oxygen, and water
# Brief Explanations:
Hydrogen ($\ce{H_2}$) and oxygen ($\ce{O_2}$) are elements (pure, one atom type). Water ($\ce{H_2O}$) is a compound (H and O bonded). Hydrogen and oxygen react to form water: $\ce{2H_2 + O_2 -> 2H_2O}$.
# Answer:
a. - Hydrogen ($\ce{H_2}$): Element (pure substance, only hydrogen atoms).
- Oxygen ($\ce{O_2}$): Element (pure substance, only oxygen atoms).
- Water ($\ce{H_2O}$): Compound (pure substance, hydrogen and oxygen atoms chemically bonded in a 2:1 ratio).
Relationship: Hydrogen and oxygen (elements) can chemically react (combine) to form water (a compound) via the reaction $\ce{2H_2 + O_2 -> 2H_2O}$.

#### Part b: Nitrogen, oxygen, and air
# Brief Explanations:
Nitrogen ($\ce{N_2}$) and oxygen ($\ce{O_2}$) are elements. Air is a mixture of them (and others) physically mixed. Nitrogen and oxygen are components of air.
# Answer:
b. - Nitrogen ($\ce{N_2}$): Element (pure substance, only nitrogen atoms).
- Oxygen ($\ce{O_2}$): Element (pure substance, only oxygen atoms).
- Air: Mixture (contains nitrogen, oxygen, carbon dioxide, etc., physically mixed, variable ratios).
Relationship: Nitrogen and oxygen (elements) are the main components of air (a mixture), mixed physically with other gases.

#### Part c: Sodium, chlorine, and table salt
# Brief Explanations:
Sodium ($\ce{Na}$) and chlorine ($\ce{Cl_2}$) are elements. Table salt ($\ce{NaCl}$) is a compound. Sodium and chlorine react to form table salt: $\ce{2Na + Cl_2 -> 2NaCl}$.
# Answer:
c. - Sodium ($\ce{Na}$): Element (pure substance, only sodium atoms).
- Chlorine ($\ce{Cl_2}$): Element (pure substance, only chlorine atoms).
- Table salt ($\ce{NaCl}$): Compound (pure substance, sodium and chlorine atoms chemically bonded in a 1:1 ratio).
Relationship: Sodium and chlorine (elements) can chemically react (combine) to form table salt (a compound) via the reaction $\ce{2Na + Cl_2 -> 2NaCl}$.

#### Part d: Carbon, water, and table sugar
# Brief Explanations:
Carbon ($\ce{C}$) is an element. Water ($\ce{H_2O}$) and table sugar ($\ce{C_{12}H_{22}O_{11}}$) are compounds (water: H and O; sugar: C, H, O). Carbon is a component of water? No, water has H and O. Wait, table sugar has carbon. Carbon (element) is a component of table sugar (compound), and water is another compound (no carbon). Wait, correction: Water ($\ce{H_2O}$) has H and O; table sugar ($\ce{C_{12}H_{22}O_{11}}$) has C, H, O. Carbon is an element; water and sugar are compounds. Carbon is a component of table sugar (since sugar has C atoms), but not of water.
# Answer:
d. - Carbon ($\ce{C}$): Element (pure substance, only carbon atoms).
- Water ($\ce{H_2O}$): Compound (pure substance, hydrogen and oxygen atoms bonded in a 2:1 ratio).
- Table sugar ($\ce{C_{12}H_{22}O_{11}}$): Compound (pure substance, carbon, hydrogen, and oxygen atoms bonded in a fixed ratio).
Relationship: Carbon (element) is one of the elements in table sugar (a compound), while water (a compound) does not contain carbon. Carbon does not react with water in a direct combination to form table sugar (sugar formation is more complex, but the key is their classifications: C is element, $\ce{H_2O}$ and sugar are compounds, with sugar containing C).

### Question 55:
#### Part a: Ammonia ($\ce{NH_3}$)
# Brief Explanations:
$\ce{NH_3}$ has N (nitrogen) and H (hydrogen) atoms, so elements are nitrogen and hydrogen.
# Answer:
a. Ammonia ($\ce{NH_3}$) contains the elements **nitrogen (N)** and **hydrogen (H)**.

#### Part b: Potassium oxide ($\ce{K_2O}$)
# Brief Explanations:
$\ce{K_2O}$ has K (potassium) and O (oxygen) atoms, so elements are potassium and oxygen.
# Answer:
b. Potassium oxide ($\ce{K_2O}$) contains the elements **potassium (K)** and **oxygen (O)**.

#### Part c: Sucrose ($\ce{C_{12}H_{22}O_{11}}$)
# Brief Explanations:
$\ce{C_{12}H_{22}O_{11}}$ has C (carbon), H (hydrogen), O (oxygen) atoms, so elements are carbon, hydrogen, oxygen.
# Answer:
c. Sucrose ($\ce{C_{12}H_{22}O_{11}}$) contains the elements **carbon (C)**, **hydrogen (H)**, and **oxygen (O)**.

#### Part d: Calcium sulfide ($\ce{CaS}$)
# Brief Explanations:
$\ce{CaS}$ has Ca (calcium) and S (sulfur) atoms, so elements are calcium and sulfur.
# Answer:
d. Calcium sulfide ($\ce{CaS}$) contains the elements **calcium (Ca)** and **sulfur (S)**.

### Question 56:
# Brief Explanations:
Element symbols are usually 1 or 2 letters. 1-letter symbols (e.g., W for wolfram) use the first letter (uppercase). 2-letter symbols (e.g., Hg for hydragyrum) use first two letters (first uppercase, second lowercase). Symbols can come from non - English names (W from German, Hg from Greek).
# Answer:
Element symbols follow a system:
- For 1 - letter symbols: The first letter (uppercase) of the element’s name (or its non - English name, like W for tungsten, from German “wolfram”).
- For 2 - letter symbols: The first two letters of the name (first uppercase, second lowercase), often from non - English names (like Hg for mercury, from Greek “hydragyrum”).

W (tungsten) is a 1 - letter symbol (from “wolfram”), uppercase. Hg (mercury) is a 2 - letter symbol (from “hydragyrum”), with first letter (H) uppercase and second (g) lowercase. This shows symbols can derive from non - English names, and follow 1 - or 2 - letter formatting (uppercase first, lowercase second for 2 - letter).

### Question 57:
# Brief Explanations:
The formula $\ce{H_2O}$ shows water has H and O elements. The subscript 2 means 2 H atoms per O atom in a water molecule. So it tells the elements (H, O) and their ratio (2:1) in the compound.
# Answer:
The formula $\ce{H_2O}$ tells us:
- **Elements**: Water is composed of the elements hydrogen (H) and oxygen (O).
- **Ratio**: In a water molecule, there are 2 hydrogen atoms for every 1 oxygen atom (the ratio of hydrogen to oxygen atoms is 2:1).
- **Composition**: It is a compound where hydrogen and oxygen are chemically bonded in a fixed 2:1 ratio.

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QUESTION IMAGE

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Explanation:

Question 52:

Answer:

Question 53:

Part a: Table salt ($\ce{NaCl}$)