Reading an Element Square
What number on the element square tells you the number of protons in an atom?
What is an Atomic Number?
Name one physical property that distinguishes most metals from nonmetals.
What are conductivity, luster, malleability, or ductility?
For main-group elements, what do elements in the same group typically have in common that causes similar chemical behavior?
What is them having the same number of valence electrons?
How many valence electrons does oxygen have?
What is 6?
What are the three main subatomic particles, and what charge does each have?
An element has an average atomic mass of 39.10 and an atomic number of 19. Approximately how many neutrons would you expect in its most common isotope?
What is 20 neutrons?
Reasoning:
39 − 19 = 20
What feature on the periodic table generally separates metals from nonmetals and helps identify the location of metalloids?
What is the zigzag/stair-step line? Metalloids are generally located along this line.
How does atomic radius generally change as you move left to right across a period, and why?
What is the atomic radius generally decreases because the increasing number of protons increases the nucleus's attraction for the electrons in the same energy level?
How do valence electrons influence whether an element tends to gain, lose, or share electrons?
Atoms tend to gain, lose, or share electrons to achieve a more stable outer electron configuration. Elements with few valence electrons often lose electrons, while those close to a full valence shell often gain electrons.
What is an isotope?
Atoms of the same element that have the same number of protons but different numbers of neutrons.
How can you determine the number of electrons in a neutral atom using the element square?
What is the number of electrons equals the atomic number?
What are two properties of metalloids that make them useful in electronics?
What are having semiconducting electrical conductivity and can have properties between metals and nonmetals? Silicon and germanium are examples.
What is the name of Group 1, and what is one characteristic property of its elements?
What are Alkali metals? They are highly reactive and have one valence electron, which they commonly lose to form +1 ions.
Describe the Bohr Model structure for chlorine. How does its number of valence electrons relate to its typical ionic charge?
Chlorine has 7 valence electrons.
It needs 1 more electron to complete its octet, so it typically gains one electron and forms Cl⁻.
Carbon-12 and Carbon-14 are isotopes of carbon. How many protons and neutrons does each isotope have?
An element square shows:
Identify the element and give the number of protons, neutrons, and electrons in its most common isotope.
What is Phosphorus-31
Aluminum is lightweight and forms a protective oxide coating. Why is aluminum still classified as a metal?
What is aluminum having metallic properties, including metallic bonding, electrical conductivity, malleability, and ductility? Its oxide coating does not change its classification.
Why can elements in Period 3 have very different chemical behaviors even though they are all in the same period?
What is them having the same number of occupied principal energy levels, but they have different numbers of valence electrons, resulting in different chemical properties?
An atom of sulfur has 6 valence electrons. What is sulfur most likely to do during a chemical reaction, and what ion would it form? Explain why.
Sulfur will most likely gain 2 electrons to complete its outer energy level. It forms a 2− ion (S²⁻).
An atom has 17 protons, 18 electrons, and 20 neutrons. Identify the element, determine whether it is an atom or ion, and state its charge.
Chlorine (Cl)
It is an ion because the numbers of protons and electrons are different.
17 protons − 18 electrons = −1 charge → Cl⁻
An element square shows:
Using this information, determine the number of protons, electrons, and neutrons in the most common isotope of this element. Then identify the element.
Bonus reasoning: The atomic number gives the number of protons and, in a neutral atom, electrons. The rounded atomic mass gives the mass number, which can be used to calculate neutrons.
Compare the electrical conductivity of sodium (Na), silicon (Si), and chlorine (Cl). What pattern do you observe moving from the metal to the metalloid to the nonmetal?
What are Na is a good conductor, Si is a semiconductor, and Cl is a poor conductor. Conductivity generally decreases moving from metals toward nonmetals.
Two elements are located in the same period but in different groups. Explain why they can have different chemical properties even though they have the same number of electron shells.
They have the same number of occupied energy levels, but they have different numbers of valence electrons. The different valence electrons cause them to have different chemical properties and reactivity.
An element has 7 valence electrons. What group is it most likely in, what does it tend to do with electrons during a chemical reaction, and what charge would its ion most likely have?
Example: Chlorine (Cl) gains one electron to become Cl⁻.
An atom has an atomic number of 12 and a mass number of 24.