Question

1. a teacher designs a demonstration to show the similarity of the physical and chemical properties of alkali metals using the procedure below.

prepare the pieces of metal and store them under oil. using the metal tweezers, remove a large piece of the alkali metal from the oil and place on a damp paper towel. place the metal on a tile and using a scalpel or sharp knife, cut pieces of lithium (5 mm cubes), sodium (4 mm cubes) and potassium (3 mm cubes). create an electrical circuit with each metal to demonstrate that alkali metals are good conductors of electricity.
which of the following is problematic about the teachers procedure?
(a) the teacher uses metal tweezers to handle the alkali metals, which will damage the low - density alkali metals.
(b) the teacher uses a damp paper towel, which will cause a reaction to occur between the alkali metals and the water held in the paper towel.
(c) the teacher uses differently sized samples of alkali metals, which will skew the results of the conductivity demonstration.
(d) the teacher uses a circuit to demonstrate conductivity, which will cause the temperature of the alkali metals to rise above their melting point.

1. which particle has the same electron configuration as a stable potassium ion?

(a) fluoride ion
(b) sodium ion
(c) neon atom
(d) argon atom
use these answers for questions 25 - 28. note that some answers may be used once, more than once, or not at all:
(a) 1s²2s²2p⁶3s²3p⁵
(b) 1s²2s²2p⁶3s²3p⁶
(c) 1s²2s²2p⁶2d¹⁰3s²3p⁶
(d) 1s²2s²2p⁶3s²3p⁶4s²3d³

1. an impossible electronic configuration
2. the ground - state configuration for the atoms of a transition element
3. the ground - state configuration of a negative ion of a halogen
4. the ground - state configuration of a common ion of an alkaline earth element

Explanation:

• Question 23: Alkali metals react vigorously with water. A damp paper towel contains water, and using it will cause a reaction between the alkali metals and water. This is a safety hazard and makes the procedure problematic.
• Question 24: A stable potassium ion (\(K^+\)) has lost one electron. Its electron configuration is \(1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}\), which is the same as that of an argon atom (\(Ar\)).
• Question 25: The \(2d\) sub - shell does not exist. So, the electron configuration \(1s^{2}2s^{2}2p^{6}2d^{10}3s^{2}3p^{6}\) is impossible.
• Question 26: Transition elements have electrons in the \(d\) sub - shell. The electron configuration \(1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}4s^{2}3d^{3}\) is for a transition element (vanadium).
• Question 27: A negative ion of a halogen (e.g., \(Cl^-\)) has an extra electron. The electron configuration \(1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}\) is similar to that of a noble gas (argon), which is the configuration of a halogen negative ion.
• Question 28: A common ion of an alkaline earth element (e.g., \(Ca^{2+}\)) has lost two electrons. The electron configuration \(1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}\) is the same as that of a noble gas (argon), which is the configuration of a common alkaline earth ion.

Answer:

• Question 23: B. The teacher uses a damp paper towel, which will cause a reaction to occur between the alkali metals and the water held in the paper towel.
• Question 24: D. argon atom
• Question 25: C. \(1s^{2}2s^{2}2p^{6}2d^{10}3s^{2}3p^{6}\)
• Question 26: D. \(1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}4s^{2}3d^{3}\)
• Question 27: B. \(1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}\)
• Question 28: B. \(1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}\)