Atomic Structure and Properties
According to Bohr’s model, how many electrons can fit in the first three energy levels?
2 in the first shell, 8 in the second, 8 in the third
When Group 1 metals touch water, they make ____________ gas and ____________ bubbles.
hydrogen,fizzy
What are valence electrons?
Electrons in the outermost shell.
What makes an object float in water?
It has a lower density than water
You can’t measure me with a ruler or string,
But drop me in water—I’ll tell you everything.
I push the water, not just a bit—
My volume shows up in every drip.
Answer: An irregular solid (measured using displacement)
An element has an atomic number of 11. Using Bohr’s model:
How many protons, neutrons, and electrons does this element have if its atomic mass is 23?
Protons: 11 (same as atomic number)
Neutrons: 23 − 11 = 12
Electrons: 11 (equal to protons in a neutral atom)
As you go down Group 1, metals react ____________ with water because their outer electron is ____________ from the nucleus and easier to ____________.
faster, farther, lose.
How do valence electrons determine how an element reacts?
They control how atoms bond (gain/lose/share)
Why do metals usually sink while wood floats?
Metals are denser than water; wood is less dense
You place a 150 g object into a cylinder. The water level rises from 100 mL to 130 mL. What is its density? Will it float in water?
Volume = 30 cm³ → Density = 150 ÷ 30 = 5 g/cm³ → It will sink
How does the number of protons in the nucleus affect atomic size across a period, based on Bohr's model?
As proton number increases across a period, nuclear charge increases, pulling electrons closer and reducing atomic size.
Which group in the periodic table is most reactive for metals, and why?
Group 1; only 1 valence electron is easily lost.
Why is helium stable despite having only 2 electrons?
It has a full first shell (2 electrons) as an outermost electron shell.
I place two eggs in two cups—
One egg floats, the other drops.
Same egg, same cup, but wait... I changed the mix.
What did I add to do this trick?
Answer: Salt (added to one cup to increase water density)
Why is it important to read the bottom of the meniscus when measuring volume in a cylinder?
Because that gives the most accurate measurement of the liquid’s true level.
I’m full but not a cup,
My outer shell is locked up.
I rarely mix or blend,
Inert, I’m nature’s friend.
What am I?
Noble gas
I’m first in my group, light as can be,
My name ends in “ium,” come test me and see.
With water I bubble and form hydrogen gas,
My reaction is slow—but I still make a splash!
Lithium
Which has a higher melting point: a substance with a simple molecular structure or a giant structure? Why?
A giant structure, because it has strong bonds throughout that require more energy to break.
Design a method to test whether an unknown object will float in a mystery liquid without directly placing it inside.
Measure the object’s density and compare it to the liquid’s density (via displacement method or mass/volume comparison). If the object’s density is lower, it will float.
You drop a solid metal into water. The water level rises by 22 mL. You know the metal’s density is 8.8 g/cm³. What is the metal’s mass?
Volume = 22 cm³; Mass = 8.8 × 22 = 193.6 g
An element has an atomic number of 17 and a mass number of 35.
a) How many protons, neutrons, and electrons does it have in a neutral atom?
b) Write its electron configuration using Bohr’s model.
c) Predict its group in the Periodic Table and explain why.
a) Protons = 17, Neutrons = 35 − 17 = 18, Electrons = 17
b) Electron configuration: 2, 8, 7
c) Group 17 (Halogens), because it has 7 electrons in its outer shell.
Explain why potassium reacts more violently with water than lithium, using atomic structure.
Potassium has more electron shells, so its outer electron is farther from the nucleus and less strongly held. This makes it easier to lose, increasing reactivity.
Why can graphite conduct electricity while diamond cannot, even though both are made of carbon?
In graphite, each carbon atom has one free electron that can move; in diamond, all electrons are tightly bonded.
You drop a sealed plastic bottle half-filled with water into a tank of fresh water. It floats. You open the cap, fill it completely with water, seal it again, and place it back in the tank. This time it sinks.
Explain why the bottle floats the first time but sinks the second time, using the concept of density.
The half-filled bottle contains both water and air, making its average density lower than water, so it floats.
When the bottle is fully filled with water, there's no more air inside. Its density becomes equal to water or slightly more (due to the bottle's own material), so it sinks.
A student places a sealed glass vial into a beaker of water. The vial floats upright, but most of it is underwater, with only 2 cm of the 10 cm height visible above the surface.
The total mass of the vial is 80 g.
The cross-sectional area is constant.
Part A: Estimate the volume of water displaced.
Part B: Use that to calculate the density of the vial.
Part C: Will the vial float in alcohol (density = 0.79 g/cm³)? Explain your reasoning.
Part A:
Volume submerged = 8 cm out of 10 → 80% of the vial is underwater.
We don't need exact volume; just the percent is enough.
Part B:
This means the vial displaces 80 cm³ of water (since it’s 80 g and floating).
So the density of the vial = mass ÷ volume = 80 g ÷ 100 cm³ = 0.8 g/cm³
Part C:
Since 0.8 > 0.79, the vial will sink in alcohol, because the liquid can’t support its density.