CA #1 Other Topics

Atomic Radii: Comparing the Size of Atoms of Deferent Elements After H and He… Fluorine is the smallest atom (top right) Francium is the largest (bottom left) This general trend is true for most elements. Mark this trend on your colored periodic charts.

F Fr

Atomic Radii: Which atom is bigger? Br or F? P or S? Does Strontium or calcium have a larger atomic radii? Sodium or chlorine? You make up two more…

Atom vs Ion size If an atom GAINS electrons it will logically become larger. So the ion formed will be bigger than the original atom. Ex. If Flourine gains an electron it will become the F -1 ion. The fluorine ion will be bigger than its original atom. Will sulfur’s ion or atom be bigger? The atom will gain 2 electrons so the S -2 ion will be bigger than the atom was.

Atom vs Ion size If an atom Loses electrons it will logically become smaller. So the ion formed will be smaller than the original atom. Ex. If lithium loses an electron it will become the Li +1 ion. The ion is smaller than the original atom. Will Calcium’s ion or atom be bigger? The atom will lose 2 electrons so the Ca+ 2 ion will be smaller than the atom was.

Answer the following… Is nitrogen’s ion or atom bigger? Is magnesium’s ion or atom bigger? Is aluminum’s ion or atom bigger? Is iodine’s atom or ion bigger?

Ionization energy (a brief introduction) It is harder to pull candy away from a strong kid than a smaller one (usually) Likewise, it is harder to take electrons away from some atoms than others. (outermost electrons) If an atoms holds on stubbornly to its electrons, it will take more energy to pull those electrons away from the atom. This energy is known as the 1 st ionization energy.

1 st ionization Energy Trend Fluorine has the highest 1st ionization energy. This means it’s hard to steal electrons from it. Why is this logical? It wants to gain electrons, not give them away! Francium is the lowest (easy to steal from). Why? Put this general trend on your Periodic Chart. Which has the higher 1 st ionization energy? In other words- which would take more energy to steal from? Na or K? Ca or Sr? Cl or F? P or As? Na or Mg? Se or Br? Rb or Sr? Te or I?

Shielding Effect (a brief introduction) Young animals that wander far from mommy are in more danger from predators than the ones that are close. Why is this? Likewise, electrons that are farthest from the nucleus are more likely to be taken. Electrons in the outermost energy level don’t feel the pull of the nucleus as much. They are more likely to be the electrons taken. Why? All the electrons BETWEEN the nucleus and the outermost elections also BLOCK THE PULL of the nucleus. This is known as the shielding effect. Class demo with people as electrons- teacher as nucleus. Also need a thief.

Which atoms will have the most shielding? Big Atoms have most shielding effect? Why? The outermost electrons are far away from the nucleus. Which of the following has the most shielding effect? Na or K? Ca or Sr? Cl or F? Ag or Pa? Rb or Sr? Pb or Lu?

Basic Metrics Review Name an object about the size of the following. Meter (m) Centimeter (cm) Kilometer (km) Millimeter (mm) Now put these in order (use prefixes only) from biggest to smallest.

Quickly Converting in the Metric King Henry loves to convert. King Henry Died Monday Drinking Chocolate Milk kilo, hecto, deca, meter or liter, deci, centi, milli (Commonly used are underlined) For example for meters and liters… Km hm dam (meter) dm cm mm Kl hl dal (liter) dl cl ml Convert 25 mm to meters Convert cm to meters Convert liters to ml Convert meters to mm Convert cm to Km Convert 26 Km to cm

A few things that will help on CA #1 Ionically bonded compounds/(called Ionic compounds) vs Covalently bonded compounds (often called covalent molecules or covalent compounds). Ionically bonded compounds have ions/charges holding them together. Ex CaCl 2 NH 4 F- this like all metals BUT… Covalent molecules/compounds have all non- metals. They don’t have ions and will have prefixes in their names. EX. OF 2 SC 4 name them both (hint:Carbide)

Why do elements in the same family have similar chemical properties? They become stable the same way! That is, Within the same family, elements lose or gain the same number of electrons when they become stable. So the are chemically similar in properties.

Cation vs Anions Cations are postive ions and are written first in ionic compounds. Ex. Anions are negative ions and are written last in ionic compunds Covlent compounds Don’t have cations or anions!

Dependent vs independent variable X or Y axis? Independent- the one the scientist controls that causes a change (on X axis when graphing). Dependent- the variable that is affected by the change in the impendent variable (on Y axis when graphing).

Precision Vs Accuracy Precision: Getting the same answer from an measurement instrument over and over. A precise instrument will give the same measurement every time. Accuracy: Getting the CORRECT (accepted) answer is getting an accurate measurement. (Just because an instrument keeps giving you the same measurement does not mean that measurement is correct! This would be precise but not accurate)

Significant Figures Precise measurement-

Rounding Final Answers (Using Significant Figures)

Significant Figures/Digits Which numbers in a measurement are significant? Ex..045 g of Au How to determine which numbers are significant figures… THE UNITED STATES Method Draw the US- the number inside Label Pacific – Atlantic P= decimal is present A= decimal is absent

Decimal Present: Rules If a decimal is PRESENT… 1) Start from the P side and approach the number (the left) 2) Keep going until you hit the first non-zero number- stop before that number. 3) This first non-zero digit and all numbers after are significant digits! (including zeros)

How many Sig. Figs.?.0034 g Ag has… 2 sig. figs mg Ca… 5 sig. figs L of oxygen… 4 sig. figs g Sr… 4 sig figs g Ti… (12 zeros) 1 sig. fig.

Decimal Absent: Rules If a decimal is Absent… 1) Start from the A (the right) side and approach the number 2) Keep going until you hit the first non- zero number- stop before that number. 3) This first non-zero digit and all numbers to the left are significant digits! (including zeros)

How many Sig. Figs.? 234 g Ag has… 3 sig. figs mg Ca… 3 sig. figs L of oxygen… 3 sig. figs mg Ti… (8 zeros) 1 sig. fig.

Rounding Answers for Multiplication and Division Problems Rule: The final ROUNDED answer must have the same number of significant figures as the measurement with the FEWEST sig figs in it. Ex m x 1.4 m = Cal= R= 33 4 sig figs 2 sig figs SSN= 3.3 x 10 1 m 2

Try a few Ex m x.078 m = Cal= OR X R= Or 2.7 X SSN = 2.7 x m 2 Ex g x 7860 L = Cal= R= SSN = 2.68 x 10 8 gL

More Practice Ex g/ g = Cal= R= 3.12 SSN = 3.12 x 10 0 (no units) Ex m /.0200 g = Cal= 1700 (2 sig. figs. currently) R= (Can’t do it without SSN) SSN = 1.70 x10 3 m/g

Round each cal. to 2 sig figs, then 3 sig figs A) g B) 3.45 g C) 67 g D) 4.5 g E) 2395 g F) g G) g H) g I) g J) g K) g R= 3.2 gR= 3.24 g R= 3.5 gR= 3.45 g R= 67 gR= 67.0 g R= 4.5 gR= 4.50 g R= 2400 gR= 2.40 x 10 3 g R= gR= g R= gR= 7.50 x 10 5 g R=.0043 gR= g R=.035 g R=.0348 g R= 3500 g R= 3.50 x 10 3 g R=.089 gR=.0887 g

Adding and Subtracting measurements Rule: The final ROUNDED answer must have the same number of digits PAST THE DECIMAL as the measurement with the Fewest Past the Decimal.

Ex g g = (fewest is 3 past decimal) Cal= 9.48 (this is only 2 past the decimal) R= 9.480g (3 past) SSN = don’t worry about for now Ex m m = Cal= 339 R= m Ex. 14 g g = Cal= R= 15g Ex g + 2.5g= Cal= R= 25.6 g