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Questions and Answers
How many significant figures are in the number 0.048?
How many significant figures are in the number 0.048?
- 3
- 4
- 1
- 2 (correct)
What is the significance of confined zeros in a number?
What is the significance of confined zeros in a number?
- They are never counted as significant figures.
- They only count if they are at the start of the number.
- Their significance depends on the context of the measurement.
- They are always counted as significant figures. (correct)
In the number 150, how many significant figures does it have if no decimal point is shown?
In the number 150, how many significant figures does it have if no decimal point is shown?
- 3
- 1
- 2 (correct)
- 4
What is the result of rounding the number 5.83298 to 3 significant figures?
What is the result of rounding the number 5.83298 to 3 significant figures?
How many significant figures are in the number 9.300?
How many significant figures are in the number 9.300?
If the first digit to be deleted when rounding is 5, what should happen to the last retained digit?
If the first digit to be deleted when rounding is 5, what should happen to the last retained digit?
What limits the precision of the number 3.1 mL?
What limits the precision of the number 3.1 mL?
Which of the following statements about trailing zeros is NOT true?
Which of the following statements about trailing zeros is NOT true?
Which statement correctly defines isobars?
Which statement correctly defines isobars?
What is the angular momentum quantum number (l)?
What is the angular momentum quantum number (l)?
Which quantum number indicates the energy level of an electron in an orbital?
Which quantum number indicates the energy level of an electron in an orbital?
If the principal quantum number (n) is increased, what effect does it have on the orbital?
If the principal quantum number (n) is increased, what effect does it have on the orbital?
What defines isotones?
What defines isotones?
The magnetic quantum number (ml) describes which of the following?
The magnetic quantum number (ml) describes which of the following?
Which of the following is a characteristic of quantum number l?
Which of the following is a characteristic of quantum number l?
Which of these quantum numbers is not derived from the Schrödinger equation?
Which of these quantum numbers is not derived from the Schrödinger equation?
Which temperature scale does not include the degree symbol in its notation?
Which temperature scale does not include the degree symbol in its notation?
What is the relationship between the Celsius and Kelvin degrees?
What is the relationship between the Celsius and Kelvin degrees?
How many degrees are between the freezing and boiling point of water in the Celsius scale?
How many degrees are between the freezing and boiling point of water in the Celsius scale?
At what temperature do Celsius and Fahrenheit equal each other?
At what temperature do Celsius and Fahrenheit equal each other?
What is the freezing point of water on the Kelvin scale?
What is the freezing point of water on the Kelvin scale?
How many degrees are there between the freezing and boiling points of water on the Fahrenheit scale?
How many degrees are there between the freezing and boiling points of water on the Fahrenheit scale?
What does the principal quantum number n represent in quantum mechanics?
What does the principal quantum number n represent in quantum mechanics?
Which quantum number indicates the shape of the orbital?
Which quantum number indicates the shape of the orbital?
Which student's results were found to be highly accurate based on given mass readings?
Which student's results were found to be highly accurate based on given mass readings?
Which conversion equation correctly relates Celsius to Fahrenheit?
Which conversion equation correctly relates Celsius to Fahrenheit?
What does the magnetic quantum number mℓ specify?
What does the magnetic quantum number mℓ specify?
What does the electron spin quantum number ms represent?
What does the electron spin quantum number ms represent?
Which of the following describes the two possible spins of an electron?
Which of the following describes the two possible spins of an electron?
What was a primary motivation behind the scientists' efforts in the mid-nineteenth century regarding the periodic table?
What was a primary motivation behind the scientists' efforts in the mid-nineteenth century regarding the periodic table?
The proposed system of chemical symbols was based on which of the following criteria?
The proposed system of chemical symbols was based on which of the following criteria?
What characterizes substances that were grouped together by early scientists?
What characterizes substances that were grouped together by early scientists?
What is the symbol of Neon?
What is the symbol of Neon?
In which group is Fluorine found in the periodic table?
In which group is Fluorine found in the periodic table?
Which element follows element 57 in the periodic table?
Which element follows element 57 in the periodic table?
What is the characteristic feature of Noble Gases?
What is the characteristic feature of Noble Gases?
What properties are generally exhibited by metals?
What properties are generally exhibited by metals?
Which element is placed in Period 6 and Group IVA?
Which element is placed in Period 6 and Group IVA?
What is true about the reactivity of Halogens?
What is true about the reactivity of Halogens?
What distinguishes Metalloids from Metals and Nonmetals?
What distinguishes Metalloids from Metals and Nonmetals?
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Study Notes
Isobars and Isotones
- Isobars: Different elements share the same atomic weight or mass number but have different atomic numbers.
- Isotones: Different elements have the same number of neutrons despite having varying atomic numbers.
Quantum Numbers
- Quantum numbers describe electron configurations in atoms derived from the Schrödinger equation.
- Principal Quantum Number (n): Indicates the energy level of an electron; values are integers (n = 1, 2, 3,...). Higher n means greater distance from nucleus.
- Angular Momentum Quantum Number (l): Determines the shape of the orbital; values range from 0 to n-1.
- Magnetic Quantum Number (ml): Describes the orientation of the orbital in space.
Significant Figures
- A measured number's significant figures indicate precision:
- Zeros can be significant (function as measures) or non-significant (function as place holders).
- Leading zeros do not count; confined zeros between nonzero digits always count; trailing zeros are significant only with a decimal point.
- Example of significant figures:
- 3456 has 4 significant figures.
- 0.048 has 2 significant figures.
- 9.300 has 4 significant figures; 150 has 2 significant figures if no decimal.
Rounding Off Numbers
- Rounding rules help retain appropriate significant figures:
- If the first omitted digit is 4 or less, drop it.
- If 5 or greater, drop and add one to the last retained digit.
Temperature Scales
- Kelvin and Celsius scales are closely related with identical degree sizes; boiling point of water is 373 K, freezing point is 273 K.
- Fahrenheit scale uses a smaller degree size, with 180 degrees between freezing (32°F) and boiling points of water.
- Temperature readings in Kelvin are always positive; no degree sign used (e.g., 350 K).
Historical Context of the Periodic Table
- Antoine Lavoisier created a system of chemical symbols and proposed an arrangement based on elemental properties.
- Elements exhibiting similar properties were grouped, aiding classification efforts.
Groups of the Periodic Table
- Soft and shiny metals are found in groups which are moderately reactive with water.
- Halogens: Group VIIA, reactive gases at room temperature.
- Noble Gases: Group VIIIA, unreactive gases, few chemical reactions.
Periodic Table Structure
- Arranged by increasing atomic number with exceptions in Groups IIIB and IVB.
- Certain elements (like Lanthanides and Actinides) are placed in separate rows at the bottom for compactness.
Characteristics of Metals, Nonmetals, and Metalloids
- Metals: Have luster, good thermal and electrical conductivity, malleability, and ductility. Most are solid at room temperature (except mercury).
- Nonmetals: Behave primarily as nonmetals chemically.
- Metalloids: Exhibit mixed properties of metals and nonmetals.
Specific Element Data
- Neon (Ne): Period 2, Group VIIIA
- Fluorine (F): Period 2, Group VIIA
- Lead (Pb): Period 6, Group IVA
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