molecular mass
A student in a lab is told to find the relative molecular mass (Mr) of methane CH4, the main component of natural gas. What is the Mr of methane?
The sum of one carbon atom 12 and four hydrogen atoms(4 x 1) = 16
A student in a lab is studying the element Lithium (Li), which is used in batteries. What is the correct electron configuration for Lithium according to the Bohr model?
Li= 2.1
A student is studying non-metals. They focus on Oxygen (O), which is essential for respiration. Question: What is the complete electron configuration for a neutral Oxygen (O) atom?
1s2,2s2,2p4
A student is studying the element Sodium, a highly reactive metal used in street lamps. How many valence electrons does Sodium have, and in which Period is it located?
1 valence electron, Period 3
A student is researching elements for fireworks. They find Strontium (Sr), which burns bright red, in Period 5, Group 2. What is the electron configuration for Strontium?
electron configuration for Strontium = 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2
In a biology class, a student is studying photosynthesis. The main product is glucose. what is the molecular mass (Mr) of glucose?
(6x Ar C) + (12 x Ar H) + (6 x Ar O)= (6x 12) + (12 x 1) + (6 x16) = 72 + 12 + 96 = 180
A biology class is discussing the importance of Magnesium (Mg), which is the central atom in chlorophyll. How many valence electrons (electrons in the outermost shell) does it have?
valence electrons of Magnesium = 2
A tech student is researching Silicon (Si), the primary element used in computer chips.
Question: Based on its configuration, how many valence electrons does a neutral Silicon (Si) atom have?
valence electrons of neutral Silicon (Si) atom = 4
A student is analyzing the element Sulfur (S), a yellow nonmetal used in gunpowder. Its electron configuration ends with the highest-energy electrons in the 3p subshell, what is the quantum number for highest-energy electron of sulfur?
the highest-energy electrons of Sulfur 3p4
the quantum number for highest-energy electrons of Sulfur n=3, l=1, ml=-1,ms=-1/2
An engineer is using a strong, light metal found in aircraft. The metal is located in Period 4, Group 4. What is the correct noble-gas electron configuration for a neutral atom?
noble-gas electron configuration for Titanium =[Ar] 4s2 3d2
A farmer wants to add nitrogen to his soil using calcium nitrate as fertilizer. To calculate how much to use, he needs its molecular mass (Mr)!
Mr CaNO3 =164.
In a lab, a student identifies a 'mystery element' that is a non-reactive gas. Its Bohr configuration is 2, 8, 8. What is this element, and what is its atomic number?
Argon (Ar), Atomic Number 18
In a nutrition class, a student learns Iron (Fe), is crucial for hemoglobin in the blood.
Question: According to Hund's rule, how many unpaired electrons are in the 3d subshell of a neutral Iron (Fe) atom?
The 6 electrons fill the 5 d orbitals, this leaves 4 electrons unpaired.
A student is given a sample of a lightweight, corrosion-resistant metal. An analysis shows its neutral atoms have the electron configuration [Ne] 3s2 3p1.What is this element, and where is it located (group and period)?
Aluminum (Al), group 3, Period 3
A student is studying Germanium (atomic number = 32), which is used in semiconductors. It is in Period 4. What is its group?
Group 14
A student in a chemistry lab uses a blue crystal, hydrated copper(II) sulfate (CuSO4.5H2O). What is the molecular mass (Mr) of this entire compound?
It's the mass of CuSO4 (159.5) plus the mass of 5 water molecules (5 x18), which equals 249.5
A student is learning about elements essential for health. An element is able to lose 2 electrons. The electron configuration for the ion of this element is 2, 8, 8. What is the element?
The element is Calcium (Ca).
A student is plating an object with a shiny metal, Copper (Cu). They look up its configuration and find it's an exception to achieve greater stability. Question: What is the correct and most stable electron configuration for a neutral Copper (Cu) atom?
[Ar] 4s1 3d10 - A full d-subshell is more stable, so one 4s electron is "promoted" to the 3d subshell.
A student is studying the halogen family, which is used in disinfectants.The element's atomic number is 53. What is its electron configuration (mechanic model)? what is period and Group of the element?
Electron configuration = 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p5
Period: 5 Group: VIIA (17)
Element = iodine
A metallurgist is analyzing Manganese (Mn), which adds strength to steel. It is located in Period 4, Group 7. What is noble-gas electron configuration of Manganese?
Manganese = [Ar] 4s2 3d5
A forensic scientist is analyzing a substance, 'Compound X', which is a hydrocarbon (contains only C and H). The mass spectrometer shows the molecular mass (Mr) is 30. Which formula matches this finding?
The molecular mass of C2H6 is (2 x 12) + (6 x 1) = 24 + 6 = 30.
A student is studying how ionic bonds form. A neutral Oxygen atom gains 2 electrons to form an oxide ion O2-.
Question: What is the electron configuration of this ion?
Electron configuration of O2- = 2.8
A student is studying how ionic bonds form. Aluminum is a metal that forms a stable ion by losing its valence electrons.
Question: What is the electron configuration of this ion?
Al3+ =1s2,2s2,2p6
A student is identifying an unknown element. They know that in its ground state, the quantum numbers for its highest-energy electron are: n=3 and l=1. The p subshell for this element is half-filled. What is this element?
Phosphorus
A student is studying enzymes that require a Mn2+ ion to function. The neutral Manganese (Mn) atom is in Period 4, Group 7. What is the resulting electron configuration for this ion?
Electron configuration for Mn2+[Ar] 3d5