aleks

What are the seven elements that are diatomic in their standard states?

H N F O I Cl Br Note for advanced students: astatine (At) and tennesine (Ts) are unstable and decay within seconds of being made. Hence their standard states are not known. However, it might be expected that, like the rest of the halogens, they would be diatomic in the standard state.

In the table below, there are descriptions of an experiment on samples of three different chemical elements. Decide whether the element is a metal or nonmetal, if you can. If there is not enough information to decide, choose can't decide in the third column. 1. Element 1 is a shiny silvery-gray solid. A 10.g cube of it is set on a hot plate. After 10 minutes, the temperature of the top of the cube has risen by less than 1°C. 2. Element 2 is a moderately soft silvery-gray solid. A small ×2cm×2cm2cm cube of it is put into a hydraulic press and squeezed until it is half as thick. When the sample is inspected, it has broken into many smaller pieces. Where the sample broke, the fresh surfaces are lighter in color. 3. Element 3 is a hard silvery-gray solid. A ×5cm5cm square of it, only 1mm thick, is flexed slightly by hand, putting a slight bend in the middle of the square.

The goal here is to learn to tell metals from nonmetals by studying a description of their macroscopic physical properties. (Metals also differ from nonmetals in their chemical properties.) There are three major types of difference you'll find useful: 1. Every metal except mercury Hg is a solid at room temperature and pressure. (Mercury is a heavy metallic-silver liquid that freezes at about −38°C.) All elements that are gases at room temperature and pressure, and the one other element that is a liquid (bromine), are nonmetals. 2. Metals are usually malleable and ductile while nonmetals are usually brittle. For example, hitting a chunk of metal will usually just dent or flatten it, while a nonmetal will often crack or shatter. 3. Metals usually have high thermal and electrical conductivity. Nonmetals are usually both thermal and electrical insulators. That is, both heat and electricity tend to flow quickly and easily through a metal, but only slowly though an nonmetal. (An important exception is graphite, one of the allotropes of carbon (a nonmetal), which conducts electricity as well as many metals.) So a good strategy here is to first consider the appearance of the sample -- gases and liquids other than mercury are automatically nonmetals. Second, consider the experiment, and ask yourself whether it tells you something about the malleability, ductility, thermal or electrical conductivity of the element. With these general ideas in mind, let's take a look at the elements you've got. In the case of Element 1, since heat flowed slowly (or not at all) from the bottom to the top of the sample, we can conclude the element has a low thermal conductivity, which is typical of nonmetals. (nonmetal) In the case of Element 2, since the sample broke under the pressure of the press instead of deforming ("losing its shape"), we can conclude the element is brittle instead of malleable, which is typical of nonmetals. (nonmetal) In the case of Element 3, since the sample bent instead of breaking, we can conclude the element is ductile, which is typical of metals. (metal)

room temperature celsius

25 degrees

families/groups on the periodic table

alkali metal- 1A alkali earth metal- 2A pnictogen- 5A chalcogen- 6A halogen- 7A noble gas- 8A

Element 2 is a grayish-white solid with a pitted surface. A small cube of it is put into a ceramic crucible and heated strongly. It melts about not far above room temperature.

can't decide in the case of Element 2, we can't really tell anything from the fact that it melted at a modest temperature. While most metals do melt at significantly higher temperatures than nonmetals, there are some with equally low melting points.

semimetals/metalloids

Elements that have characteristics of both metals and non-metals

Element is a moderately soft silvery-gray solid. A square of it, only thick, is heated with a flame at one end. The square becomes warm and starts to soften all over.

In the case of Element , since heat flowed quickly from the edge of the square to all the rest of the sample, we can conclude the element has a high thermal conductivity, which is typical of metals.

ecide which element probably has a density most and least similar to the density of rubidium. options are fluorine, cesium, thallium, & indium.

Metals are more similar to each other than they are to nonmetals. Likewise, nonmetals are more similar to each other than they are to metals. Elements in the same group of the Periodic Table are most similar to each other You can use the Periodic Table to find out that rubidium, cesium, thallium, and indium are all metals, while fluorine is a nonmetal. That means fluorine is going to be least similar to rubidium. To choose whether cesium, thallium, or indium is more similar to rubidium, compare their positions in the Periodic Table: You can see that cesium is in the same group (Group 1A) as rubidium, while thallium and indium are in another group (Group 3A). That means cesium is going to be most similar to rubidium.

Neutron (symbol, charge, mass)

N0, 0, 1.0 amu

Write the chemical symbols for three different atomic cations that all have 24 protons.

Since all three chemical symbols you are asked to write will represent an atom with 24 protons, they must all represent atoms of element number 24. So, first find element 24 in the Periodic Table. It's chromium, with the chemical symbol Cr. Because all the chromium atoms will be cations they will all have a positive charge. The smallest possible positive charge is +1. The largest possible positive charge on an atom of chromium is +24, which would be the charge if the chromium ion had no electrons at all. However, it is rare for cations seen in ordinary chemistry to have charges greater than about +5. So reasonable charges for your cations lie between +1 and +5. One possible answer is Cr+, Cr5+, Cr3+

What are the blocks of the Periodic Table?What is an s-block element? What is a p-block element? What is a d-block element?

The Periodic Table can be divided into four blocks, like so: Note: For our purposes here, we must move helium over next to hydrogen. These blocks are called the s-block (Groups 1A, 2A and helium), the p-block (Groups 3A through 8A except helium), the d-block (the transition elements except the lanthanides or actinides) and the f-block (the lanthanides and actinides). An element in the s-block is called an s-block element, and so forth. For example, carbon (symbol C) is a p-block element, while iron (Fe) is a d-block element. The names of the blocks come from the electron subshell in which the valence electrons lie. For example, s-block elements like Li or Ca have 1 or 2 valence electrons in an s subshell. Chemists often find it useful to know the block in which an element lies, because there are many properties that elements in the same block tend to share. For example, all the nonmetals except hydrogen lies in the p block. All the metals in the s-block tend to be highly reactive, soft, and low-melting, while their counterparts in the d-block tend to be less reactive, hard, and high-melting.

a penny has a mass of 2.50 g and the moon has a mass of 7.35 x 10^22 kg What is the mass of 1 mole of pennies?Round your answer to 3 significant digits. How many moles of pennies have a mass equal to the mass of the Moon? Round your answer to 3 significant digits.

The mole is an SI unit of number. This is how it's defined: A carbon atom is very, very small, so there are a lot of carbon atoms in grams of carbon-12. So many, in fact, that the exact number, called the Avogadro Number (symbol Na ), is only known to within about ten trillion: Na = 6.0221419947... x 10^23 (you don't usually need to use all these digits, five is plenty when using ALEKS) The number of any type of object can be measured in moles. A mole of carbon atoms is Na carbon atoms, a mole of carbon dioxide molecules is Na carbon dioxide molecules, and a mole of cabbages is Na cabbages. With those general ideas in mind, let's answer the specific questions you were asked: If one penny has a mass of 2.50 g , then the mass of an Avogadro number of them must be Na times bigger (2.50 g)(6.02214 x 10^23) = 1.51 x 10^24 g This is the mass of mole of pennies. A chemist would call this the molar mass of pennies. To calculate how many moles of pennies have the same mass as the Moon, you just need to divide the mass of the Moon by the molar mass of pennies: refer to photo Notice that you can count huge numbers of tiny things just by weighing them, if you know their molar mass. You can just weigh out how much you want, and divide by the molar mass to find the number of moles you have. This is why chemists measure the numbers of atoms and molecules in moles, and why knowing the molar mass of elements and compounds is very important.

What is the standard state of an element?

The standard state of an element is how the pure element is found at pressure of 105 Pa (very close to 1 atm) and a standard temperature, usually 25°C. The standard state is often written as a chemical formula to show the chemical state of the element, followed by a physical state symbol to show the physical state of the element. The standard states of the elements can be summarized by this chart: In other words, the metals except for mercury (Hg) are solids in their standard state. Mercury is a liquid. Most nonmetals are written as simple solids, except for the noble gases the seven diatomic nonmetals, phosphorus, and sulfur. The diatomic nonmetals are mostly gases, but iodine is a solid and bromine is a liquid. As an example, let's ask what the standard state of helium would be. Helium is a noble gas, so its standard state is He(g). That is, helium in its standard state is a monatomic gas. What is the standard state of chlorine? Chlorine is one of the seven diatomic nonmetals, so it's standard state is Cl2(g). That is, chlorine in its standard state is a diatomic gas. Bromine is also one of the seven diatomic nonmetals, but it's specially listed: its standard state is Br2(l). So bromine in its standard state is a diatomic liquid.

potential energy

You can solve this problem by using three facts about how the electrostatic potential energy of a collection of charged objects depends on the charge and separation of the objects (see graph at right). First, the potential energy of a pair of charges is positive if they are like charges, and negative if they are unlike charges. Notice that this means the potential energy of a pair of like charges is always higher than the potential energy of a pair of unlike charges. Second, the magnitude of the potential energy decreases with the separation between the charges (see sketch at right). That is, the potential energy of a pair of unlike charges gets less negative as the separation between them increases, and the potential energy of a pair of like charges gets less positive. (That means when the pair gets very far apart, the potential energy approaches zero for both like and unlike charges.) For example, the potential energy of a +1 charge and a +2 charge becomes more positive if they get closer. On the other hand, the potential energy of a +1 charge and a −2 charge gets more negative if they get closer. Finally, the magnitude of the potential energy grows with the product of the charges. That is, the potential energy of a pair of unlike charges gets more negative as the product of the charges increases, and the potential energy of a pair of like charges gets more positive. For example, the potential energy of a +1 and +2 charge is more positive than the potential energy of a +1 and +1 charge separated by the same distance. On the other hand, the potential energy of a +1 charge and a −2 charge is more negative than the potential energy of a +1 charge and a −1 separated by the same distance.

electron (symbol, charge, mass, location)

e-, -1, .000549 amu or 1/1800 amu, orbiting around nucleus

physical properties non metals

gas or network solid at 25 C transparent or strongly colored, not reflective even when polished brittle (breaks before bending). Usually weak, except for network solids electrical conductivity: poor thermal conductivity: poor, except for network solids Note: these are only typical properties of metals and nonmetals, and there are many exceptions. Furthermore, the properties of elements change gradually from one side of the Periodic Table to the other, and elements close to the metal-nonmetal dividing line, often called semimetals or metalloids, usually have properties in between those of typical metals and those of typical nonmetals.

Element 2 is a shiny silvery-gray solid. A 5 cm x 5 cm square of it, only 1mm thick, is pressed into a dish-shaped mold under high pressure. When the sample is removed, it has become lighter in color and now has the shape of the mold.

metal

Element 3 is a moderately soft silvery-gray solid. A 5 cm x 5 cm square of it, only 1mm thick, is heated with a flame at one end. The square becomes warm and starts to soften all over.

metal (conducts heat)

physical properties metals

metallic solid at 25 C Silvery-white or gray, shiny, reflective when polished. Malleable (bends without breaking), and ductile (stretches before breaking). Usually strong, except for Group 1A metals. melting point: well above room temp electrical conductivity: good thermal conductivity: good note- these are only typical properties of metals and nonmetals, and there are many exceptions. Furthermore, the properties of elements change gradually from one side of the Periodic Table to the other, and elements close to the metal-nonmetal dividing line, often called semimetals or metalloids, usually have properties in between those of typical metals and those of typical nonmetals

Element 1 is a moderately soft yellow solid. A small 2 cm x 2 cm x 2 cm cube of it is put into a hydraulic press and squeezed until it is half as thick. When the sample is inspected, it has broken into many smaller pieces. Where the sample broke, the fresh surfaces are lighter in color.

nonmetal

proton (symbol, charge, mass, location)

p+, +1, 1.0 amu, nucleus

chemical properties nonmetals

reaction with metals: Combination reaction that forms an ionic compound. reaction with non-metals: Combination reaction that forms a molecular compounds. electronegativity: high typical atomic ions: anions typical oxidation states: Negative in ionic compounds, positive or negative in molecular states compounds usual role in oxidation-reduction reaction: oxidizer reaction with oxygen: form acidic oxide reaction with hydrogen: Form molecular compound with H in the +1 oxidation state. Note: these are only typical properties of metals and nonmetals, and there are many exceptions. Furthermore, the properties of elements change gradually from one side of the Periodic Table to the other, and elements close to the metal-nonmetal dividing line, often called semimetals or metalloids, usually have properties in between those of metals and those of nonmetals.

chemical properties metals

reaction with metals: Single or double displacement reactions, in which one metal oxidizes and reduces the other reaction with nonmetals: Combination reaction that forms an ionic compounds. electronegativity: low typical atomic ions: cations typical oxidation states: + usual role in oxidation-reduction reaction: reducing agent reaction with oxygen: form basic oxide reaction with hydrogen: form ionic compound containing the hydride (H-) anion Note: these are only typical properties of metals and nonmetals, and there are many exceptions. Furthermore, the properties of elements change gradually from one side of the Periodic Table to the other, and elements close to the metal-nonmetal dividing line, often called semimetals or metalloids, usually have properties in between those of metals and those of nonmetals.