MS-Matter-U1L1S1-3

​Performance Expectation

MS-PS1-1 I can develop models (ex. drawings, 3D ball and stick structures, or computer representations showing different molecules with different types of atoms) to describe the atomic composition of simple molecules and extended structures.

Multiple Choice

a unique particle of matter that is a fundamental building block of matter

• atom

• element

• atomic mass

Multiple Choice

an individual particle of an element

• atom

• atomic mass

• element

Multiple Choice

the requirements that must be met for an engineering solution to be successful

• constraint

• criteria

Multiple Choice

the mass of a single atom; all atoms of an element have approximately the same atomic mass.

• element

• atomic mass

• atom

Multiple Choice

a limitation on the range of possible solutions to a design

• criteria

• constraint

• requirement

Multiple Choice

a table that lists all of the known elements and groups them into columns by important shared properties

• atomic mass

• periodic table of the elements

• chemical symbol

Multiple Choice

a shorthand notation of one, two, or three letters that represent the name of the element

• Atom

• chemical symbol

• periodic table of the elements

Open Ended

Look carefully at the list of objects and order them from smallest to largest.

ant

atom

cell

dust particle

ping pong ball

​3. Classifying Elements

​Well before scientists could see the individual atoms, scientists were finding ways to study, identify, and classify elements. If you had to organize your closet, how would you do it?

Open Ended

How would scientists classify elements if they could not see what their different atoms looked like?

​ In the early 1800s, a German scientist named Johann Döbereiner noticed an interesting pattern with certain elements. He observed that lithium, sodium, and potassium are all soft, gray metals. He also noticed that all three elements react with water. He grouped these three elements together based on their property of reacting with water. However, they do not react in the exact same way. Pure lithium only fizzes when exposed to water. Pure sodium can react violently enough to create a fire when mixed with water. Pure potassium practically explodes when wet.

​Some groups of three elements with similar properties show a pattern in which, when arranged in order by atomic mass, the middle element has properties that are in between the properties of the other two. The trio of metal elements lithium, sodium, and potassium are similar in appearance. All three react with water, but they do so to different degrees.

​Döbereiner then looked at the atomic masses of these three elements. The atomic mass is the mass of a single atom; all atoms of an element have approximately the same atomic mass. Scientists report atomic mass in a unit of measurement called daltons (Da). The atomic mass of hydrogen is 1 Da. Oxygen's is 16 Da.

Open Ended

Define atomic mass and name what unit of measure is used for atoms.

​When Döbereiner arranged lithium, sodium, and potassium in increasing order by atomic mass, the middle element, sodium, had an atomic mass that was almost exactly halfway between the atomic masses of the other two elements. He noticed that sodium's atomic mass, 23 Da, is close to that of the average of lithium's (7 Da) and potassium's (39 Da). He used his observations and their atomic mass to predict that the middle element in this type of group would react and behave as an intermediate of the other two.

Open Ended

Copper, silver, and gold are three elements often grouped together. They are also often called coinage metals. Why do you think that is?