Transition Elements

Transition Elements

• Groups 3–12, which are transition elements, are all metals.

• Their properties change less than the representative elements.

• The elements in the iron triad are iron, cobalt, and nickel.

Inner Transition Elements

• The lanthanide series contains elements from cerium to lutetium.

• The lanthanides also are known as the rare earth elements.

• The actinide series contains elements from thorium to lawrencium.

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Representative Elements

Groups 1 and 2

• Groups 1 and 2 elements are always combined with other elements.

• The elements in Groups 1 and 2 are all metals except for hydrogen.

• Alkaline earth metals are not as active as the alkali metals.

Groups 13–18

•With Groups 13–18, a single group can contain metals, nonmetals, and metalloids.

• Nitrogen and phosphorus are required by living things.

• The halogen group will form salts with alkali metals.

Introduction to the Periodic Table

Development of the Periodic Table

                 Emade coins and jewelry from gold and silver. They also made tools and weapons from copper, tin, and iron. In the nineteenth centuryarly civilizations were familiar with a few of the substances now called elements. They , chemists began to search for new elements. By 1830, they had isolated and named 55 different elements. The list continues to grow today.

Dmitri Mendeleev published the first version of the periodic table in 1869. Mendeleev left three gaps on the periodic table for missing elements.

Moseley arranged Mendeleev’s table according to atomic number, not by atomic mass.

Today’s Periodic Table

• The periodic table is divided into sections.

• A period is a row of elements whose properties change gradually and predictably.

• Groups 1 and 2 along with Groups 13–18 are called representative elements.

• Groups 3–12 are called transition elements.

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Physical and Chemical Properties

Physical Properties

                 It’s a busy day at the state fair as you and your classmates navigate your way through the crowd. While you follow your teacher, you can’t help but notice the many sights and sounds that surround you. Eventually, you fall behind the group as you spot the most amazing ride you have ever seen. You inspect it from one end to the other.How will you describe it to the group when you catch up to them? What features will you use in your description?

                 Perhaps you will mention that the ride is large, blue, and made of wood. These features are all physical properties, or characteristics, of the ride.A physical property is a characteristic that you can observe without changing or trying to change the composition of the substance. How something looks, smells, sounds, or tastes are all examples of physical properties. In Figure 1 you can describe and differentiate all types of matter by observing their properties.

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Figure 1

Chemical Properties

                 Some properties of matter cannot be identified just by looking at a sample. For example, nothing happens if you look at thematches in the first picture. But if someone strikes the matches on a hard, rough surface they will burn, as shown in the second picture. The ability to burn is a chemical property. A  chemical property is a characteristic that cannot be observed without altering the substance.As you can see in the last picture, the matches are permanently changed after they are burned. Therefore this property can be observed only by changing the composition of the match.Another way to define a chemical property, then, is the ability of a substance to undergo a change that alters its identity. You will learn more about changes in matter in the following section.

Source: Glencoe Science-The Nature of Matter-SE_0078617650

Behaviour of Fluids

Pressure

It’s a beautiful summer day when you and your friends go outside to play volleyball, much like the kids in  Figure 1. There’s only one problem—the ball is flat.You pump air into the ball until it is firm. The firmness of the ball is the result of the motion of the air particles in the ball. As the air particles in the ball move, they collide with one another and with the inside walls of the ball. As each particle collides with the inside walls, it exerts a force, pushing the surface of the ball outward. A force is a push or a pull. The forces of all the individual particles add together to make up the pressure of the air. Pressure is equal to the force exerted on a surface divided by the total area over which the force is exerted.

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When force is measured in newtons (N) and area is measured in square meters (m2), pressure is measured in newtons per square meter (N/m2). This unit of pressure is called a pascal (Pa). A more useful unit when discussing atmospheric pressure is the kilopascal (kPa), which is 1,000 pascals.

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Figure 1

Force and Area

You can see from the equation on the opposite page that pressure depends on the quantity of force exerted and the area over which the force is exerted. As the force increases over a given area, pressure increases. If the force decreases, the pressure will decrease. However, if the area changes, the same amount of force can result in different pressure. Figure 2 shows that if the force of the ballerina’s weight is exerted over a smaller area, the pressure increases. If that same force is exerted over a larger area, the pressure will decrease.

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Figure 2

Changes in Gas Pressure

In the same way that atmospheric pressure can vary as conditions change, the pressure of gases in confined containers also can change. The pressure of a gas in a closed container changes with volume and temperature.

Pressure and Volume

If you squeeze a portion of a filled balloon, the remaining portion of the balloon becomes more firm. By squeezing it, you decrease the volume of the balloon, forcing the same number of gas particles into a smaller space. As a result, the particles collide with the walls more often, thereby producing greater pressure. This is true as long as the temperature of the gas remains the same. You can see the change in the motion of the particles in  Figure 3. What will happen if the volume of a gas increases? If you make a container larger without changing its temperature, the gas particles will collide less often and thereby produce a lower pressure.

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Figure 3

Float or Sink

You may have noticed that you feel lighter in water than you do when you climb out of it. While you are under water, you experience water pressure pushing on you in all directions. Just as air pressure increases as you walk down a mountain, water pressure increases as you swim deeper in water. Water pressure increases with depth. As a result, the pressure pushing up on the bottom of an object is greater than the pressure pushing down on it because the bottom of the object is deeper than the top. The difference in pressure results in an upward force on an object immersed in a fluid, as shown in Figure 4. This force is known as the buoyant force. If the buoyant force is equal to the weight of an object, the object will float. If the buoyant force is less than the weight of an object, the object will sink.

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Figure 4

Archimedes’ Principle

What determines the buoyant force? According to Archimedes’ (ar kuh MEE deez)  principle, the buoyant force on an object is equal to the weight of the fluid dis- placed by the object.  In other words, if you place an object in a beaker that already is filled to the brim with water, some water will spill out of the beaker.

Pascal’s Principle

What happens if you squeeze a plastic container filled with water? If the container is closed, the water has nowhere to go. As a result, the pressure in the water increases by the same amount everywhere in the container—not just where you squeeze or near the top of the container. When a force is applied to a confined fluid, an increase in pressure is transmitted equally to all parts of the fluid. This relationship is known as Pascal’s principle.

 Source:  Glencoe Science-The Nature of Matter-SE_0078617650

Changes of State

Thermal Energy and Heat

Shards of ice fly from the sculptor’s chisel. As the crowd looks on, a swan slowly emerges from a massive block of ice. As the day wears on, however, drops of water begin to fall from the sculpture. Drip by drip, the sculpture is transformed into a pud- dle of liquid water.What makes matter change from one state to another? To answer this question, you need to think about the particles that make up matter.

Energy

Simply stated, energy is the ability to do work or cause change. The energy of motion is called kinetic energy. Particles within matter are in constant motion. The amount of motion of these particles depends on the kinetic energy they possess. Particles with more kinetic energy move faster and farther apart. Particles with less energy move more slowly and stay closer together. The total kinetic and potential energy of all the particles in a sample of matter is called thermal energy. Thermal energy, an extensive property, depends on the number of particles in a substance as well as the amount of energy each particle has. If either the number of particles or the amount of energy in each particle changes, the thermal energy of the sample changes. With identically sized samples, the warmer substance has the greater thermal energy. In Figure 2, the particles of hot water from the hot spring have more thermal energy than the particles of snow on the surrounding ground.

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Figure 1

Temperature

Not all of the particles in a sample of matter have the same amount of energy. Some have more energy than others. The average kinetic energy of the individual particles is the temperature, an intensive property, of the substance.You can find an average by adding up a group of numbers and dividing the total by the number of items in the group. For example, the aver- age of the numbers 2, 4, 8, and 10 is (2  4  8  10)  4  6. Temperature is different from thermal energy because thermal energy is a total and temperature is an average. You know that the iced tea is colder than the hot tea, as shown in Figure 2. Stated differently, the temperature of iced tea is lower than the temperature of hot tea. You also could say that the average kinetic energy of the particles in the iced tea is less than the average kinetic energy of the particles in the hot tea.

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Figure 2

Heat

When a warm object is brought near a cooler object, thermal energy will be transferred from the warmer object to the cooler one. The movement of thermal energy from a substance at a higher temperature to one at a lower temperature is called heat. When a substance is heated, it gains thermal energy. Therefore, its particles move faster and its temperature rises. When a substance is cooled, it loses thermal energy, which causes its particles to move more slowly and its temperature to drop.

Specific Heat

As you study more science, you will discover that water has many unique properties. One of those is the amount of heat required to increase the temperature of water as compared to most other substances. The specific heat of a substance is the amount of heat required to raise the temperature of 1 g of a substance 1°C. Substances that have a low specific heat, such as most metals and the sand in Figure 3, heat up and cool down quickly because they require only small amounts of heat to cause their temperatures to rise. A substance with a high specific heat, such as the water in  Figure 3, heats up and cools down slowly because a much larger quantity of heat is required to cause its temperature to rise or fall by the same amount.

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Figure 3

VISUALIZING STATES OF MATTER

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Source: Glencoe Science-The Nature of Matter-SE_0078617650

 

 

Matter

What is matter?

Take a look at the beautiful scene in Figure 1.What do you see? Perhaps you notice the water and ice.Maybe you are struck by the Sun in the background. All of these images show examples of matter. Matter is anything that takes up space and has mass. Matter doesn’t have to be visible—even air is matter.

States of Matter All matter is made up of tiny particles, such as atoms, molecules, or ions. Each particle attracts other particles. In other words, each particle pulls other particles toward itself. These particles also are constantly moving. The motion of the particles and the strength of attraction between the particles determine a material’s state of matter.

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Figure 1

There are three familiar states of matter—solid, liquid, and gas. A fourth state of matter known as plasma occurs at extremely high temperatures. Plasma is found in stars, lightning, and neon lights. Although plasma is common in the universe, it is not common on Earth.

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                                                              Gases

Source: Glencoe Science-The Nature of Matter-SE_0078617650